Polishing pad, and method and apparatus for polishing

ABSTRACT

A polishing pad characterized by having a mechanism for supplying water to the plane of the polishing pad in contact with the article to be polished, in particular, in case the mechanism comprises a domain structure having an area of 1×10 −6  m 2  or smaller, reduces the generation of scratches and the dust adhesion on the surface of the article to be polished, while increasing polishing rate at low dishing and erosion; hence, the product is applicable to the field of surface polishing of semiconductor thin films.

TECHNICAL FIELD

The present invention relates to a polishing pad for use in chemicalmechanical polishing (CMP), in which the article to be polished ispressed against a rotating elastic pad to thereby establish relativemotion while supplying thereto a polishing liquid containing processingabrasives or a polishing liquid free from abrasives, therebypreferentially polishing the protruded portion of an irregular surfaceof the article to be polished with an abrasive; the invention alsorelates to a polishing apparatus and polishing method using the same.

BACKGROUND ART

In producing a semiconductor having highly increased degree ofintegration, the surface of the dielectric film should be completelyplanarized to realize multilayer wiring. As representative techniques ofplanarization known heretofore, studies have been made on, for instance,SOG (Spin-On-Glass) process, etch-back process (P. Elikins, K.Reinhardt, and R. Layer, “A planarization process for double metal CMOSusing Spin-on Glass as a sacrificial layer”, Proceeding of 3rdInternational IEEE VMIC Conf., 100 (1986)), and lift-off process (K.Ehara, T. Morimoto, S. Muramoto, and S. Matsuo, “Planar InterconnectionTechnology for LSI Fabrication Utilizing Lift-off Process”, J.Electrochem. Soc., Vol.131, No.2, 419 (1984)).

Concerning the SOG process, although this is a planarization processutilizing the fluidity of the SOG film, the film itself is impossible torealize complete planarization. The etch-back process is the most widelyemployed technique; however, this process suffers the problem ofgenerating dust on etching the resist and the dielectric film at thesame time, and is not an easy technique concerning the point of dustcontrol. In the lift-off process, the stencil material used cannot becompletely dissolved on lift-off, and this leads to the generation of aproblem of not realizing lifting off. Hence, this process is not putinto practice due to incomplete controllability and production yield.

In the light of the aforementioned circumstances, CMP method is beingattracting attention. This process comprises preferentially polishingthe protruded portion of an irregular surface of the article to bepolished with an abrasive by pressing the article to be polished againsta rotating elastic pad, to thereby establish relative motion whilesupplying thereto a polishing liquid containing processing abrasives ora polishing liquid free from abrasives, and this process is widelyemployed thanks to the simplicity of the process.

For instance, Japanese Patent Laid-Open No. 11050/1996 discloses apolishing cloth characterized in that it comprises parts differing insurface hardness are formed by utilizing phase separation of a resin.However, the problems of scratches and dust adhesion remain to besolved. Furthermore, this process suffers the disadvantage that thehomogeneous processing is difficult with respect to the thicknessdirection of the polishing cloth.

Further recently, fine irregularities that are present on thesemiconductor wafer itself before subjecting it to the surfaceroughening process, i.e., those expressed as waviness, nanotopology andthe like, which were conventionally unknown as problems, are nowregarded problematic, and hence, practiced at present are the doubleface polishing, a process of carrying out polishing while flowing analkali, and the like. However, in the CMP processes above, there arementioned problems occurring on the surface of the article to bepolished, such as the scratches, adhesion of dust, incomplete globalplanarity, and the like.

The polishing pads can be roughly classified into polishing pads for usein a conventional CMP in which polishing is carried out while supplyinga polishing liquid containing abrasives (which is simply referred tohereinafter as “polishing pad” unless particularly specified), and padswith fixed abrasives, in which polishing is carried out while supplyinga polishing liquid free of abrasives.

As common problems to be solved for the two types of pads above, therecan be mentioned the generation of scratches and the adhesion of dust.

With respect to the so-called dishing and erosion on polishing, it issaid that pads with fixed abrasives are superior, however, the problemsof the scratches and the adhesion of dust that generate on the surfaceof the article to be polished remain unsolved.

In case the adhesion of dust or scratches generate on the polishingsurface of, for instance, interlayer dielectric film and the like, stepfailure and the like may generate on forming interconnection using an Albased metal and the like in the later process, and this may lead to thegeneration of a problem of causing loss of reliability, such as thedegradation in the resistance against electromigration. Otherwise, onpolishing a non-magnetic substrate for HDD (Hard Disk Drive) and thelike, this causes a drop in reproduced signals, such as dropouts. Thegeneration of scratches are believed to be attributed to theagglomerates due to poor dispersion of abrasives. In particular, thepolishing slurry using alumina as the abrasive grains, which is employedin the CMP of metallic films, suffers poor dispersibility, and is farfrom complete in preventing scratches from generating. Concerning dustadhesion, even the cause thereof is yet unknown.

In common sense, the use of a hard polishing pad is preferred forimproving global planarity; however, since dust adhesion or scratchestend to form more easily by the use of such hard polishing pad, it isbelieved impossible to satisfy both requirements at the same time. Forinstance, although such attempts are disclosed in International PatentPublication No. 500622/1996 or in Japanese Patent Laid-Open No.2000-34416, prevention of dust adhesion and scratches is not concurrentwith the planarization characteristics.

In the light of such circumstances, an object of the present inventionis, particularly, to reduce dust adhesion on the surface of the polishedarticle. Another object of the present invention is to reduce thegeneration of scratches, while yet achieving favorable planarizationcharacteristics at the same time.

Furthermore, another object is to remove, by a simple polishing method,fine irregularities of the semiconductor wafer itself before subjectingit to the surface roughening process, i.e., those expressed as waviness,nanotopology and the like.

DISCLOSURE OF THE INVENTION

The present invention comprises constitutions as follows.

-   (1) A polishing pad characterized by that it comprises a mechanism    for supplying water to the plane of the polishing pad in contact    with the article to be polished.-   (2) A polishing pad as described in (1) above, wherein the mechanism    for supplying water is characterized in that it comprises a domain    structure having an area of 1×10⁻⁶ m² or smaller.-   (3) A polishing pad as described in (1) or (2) above, wherein the    mechanism for supplying water is characterized in that it is    hydrophilic, and that it has a complex structure comprising a    substantially water-insoluble polymer and a resin matrix.-   (4) A polishing pad as described in (3) above, wherein the polymer    substantially insoluble to water is characterized in that it    comprises hydrophilic organic particles and/or fibrous material    having a water absorptivity of 5000% or lower.-   (5) A polishing pad as described in (4) above, wherein said    particles and/or fibrous material are characterized in that they are    mixed in such a manner to account for 4 wt. % or higher but not    higher than 60 wt. %.-   (6) A polishing pad as described in (3) above, wherein the    hydrophilic polymer substantially insoluble to water is    characterized in that it is a sheet-like material, and comprises a    laminate of a complex structure with an organic polymer matrix.-   (7) A polishing pad as described in (6) above, wherein the    sheet-like material is characterized in that it comprises at least    one of non-woven-like, textile-like, woven-like, felt-like, porous    membrane-like, film-like, and sponge-like sheet.-   (8) A polishing pad as described in (6) or (7) above, wherein the    layers constituting the laminate are characterized in that each has    a thickness of 1 μm or more.-   (9) A polishing pad as described in (6) to (8) above, wherein the    pad is characterized in that the resin content and/or the type of    the resin of the resin matrix differs from layer to layer.-   (10) A polishing pad as described in (6) to (9) above, wherein the    pad is characterized in that the thickness and/or the type of the    sheet-like material differs from layer to layer.-   (11) A polishing pad as described in (6) to (10) above, wherein it    is characterized in that the sheet-like material accounts for 3 wt.    % or more.-   (12) A polishing pad as described in (3) above, wherein the    hydrophilic polymer substantially insoluble to water is    characterized in that it comprises a fibrous material having an    aspect ratio of 5 or higher and/or particles formed from the    composite thereof.-   (13) A polishing pad as described in (3) to (12) above, wherein the    hydrophilic polymer substantially insoluble to water is    characterized in that it has nominal water content of 3% or higher.-   (14) A polishing pad as described in (3) to (13) above, wherein it    is characterized in that, on taking the centerline average roughness    Ra of a single silicon wafer having provided with an oxide film    after polishing, the difference in value of Ra falls in a range of    0.2 μm or less with respect to the surface roughness profile    generated by dressing before polishing taken as the standard.-   (15) A polishing pad as described in (3) to (13) above, wherein the    hydrophilic polymer substantially insoluble to water is    characterized in that it is mixed in such a manner substantially    free from interstices.-   (16) A polishing pad as described in (1) to (15) above, wherein the    matrix constituting the pad is characterized in that it is made of a    thermosetting resin.-   (17) A polishing pad as described in (3) to (16) above, wherein the    pad is characterized in that it has interstices in addition to the    hydrophilic polymer substantially insoluble to water.-   (18) A polishing pad as described in (1) to (17) above, wherein the    pad is characterized in that it comprises inorganic fine particles.-   (19) A polishing pad as described in (18) above, wherein the pad is    characterized in that it comprises organic-inorganic nanocomposite    and/or barium carbonate particles.-   (20) A polishing pad as described in (18) or (19) above, wherein the    organic-inorganic nanocomposite is characterized in that it is at    least one selected from a combination of a phenolic resin and silica    particles, a combination of an epoxy resin and silica particles, and    a combination of a polyamide resin and silica particles.-   (21) A polishing pad as described in (1) to (20) above, wherein the    pad is characterized in that it further comprises a water-soluble    substance.-   (22) A polishing pad as described in (21) above, wherein the pad is    characterized in that the water-soluble substance accounts for 0.01    wt % to 10 wt %.-   (23) A polishing pad as described in (1) to (22) above, wherein the    pad is characterized in that it yields a D hardness of 65 or higher.-   (24) A polishing pad as described in (1) to (23) above, wherein the    pad is characterized in that it yields a flexural modulus of    elasticity of 0.5 GPa or higher but not higher than 100 GPa.-   (25) A polishing pad as described in (1) to (24) above, wherein the    pad is characterized in that it yields a one-hour water absorptivity    of 0.8% or higher but not higher than 15%.-   (26) A polishing pad as described in (1) to (25) above, wherein the    pad is characterized in that the water absorption rate within 5    minutes from contact with water is 3%/hr or higher.-   (27) A polishing apparatus characterized in that it used a polishing    pad described in one of 1 to 26 described above.-   (28) A polishing method characterized in that it used a polishing    pad described in one of 1 to 26 described above.-   (29) A method for producing a semiconductor wafer or a semiconductor    chip, characterized in that processing is carried out by using a    polishing pad described in one of 1 to 26 described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a 4-inch diameter wafer provided with anoxide film.

FIG. 2 is a diagram showing the interconnection pattern on an oxide filmTEG.

BEST MODE FOR CARRYING OUT THE INVENTION

The polishing pad according to the present invention comprises amechanism for supplying water to the interface that is formed betweenthe pad and the article to be polished being pressed against the pad.

The domain structure as referred in the present invention is a physicalstructure and/or a chemical structure, which, in case the polishing padis pressed against the article to be polished, maintains a water layerin the interface. As a matter of course, the domain structure may be asingle physical structure. By having such a mechanism, the adhesion ofdust to the surface of the article to be polished can be minimized.Concerning the size of the domain in this mechanism, a larger domain isbetter, however, too large a domain excessively decreases the mechanicalstrength of the pad surface as a polishing pad as to considerablydecrease the durability when polishing, and this leads to a new problemof making it difficult to sufficiently achieve the desired polishingrate. The threshold value for the size differs depending on the resinmainly constituting the pad, however, it has been found that thisdisadvantage can be circumvented by setting the area to 1×10⁻⁶ m² orsmaller. The polishing characteristics are not particularly affected bywhether the domain size is large or small; however, from the viewpointof shapability of the polishing pad and of the difficulty in suppressingthe fluctuation in quality, the domain size is preferably 1×10⁻¹⁴ m² orlarger. It is one solution to establish a so-called microscopic phaseseparation structure, but it is difficult to maintain the same state forthe surface and the inside of the polishing pad, and hence, it isextremely difficult to control the micro phase separation structure overthe entire film thickness. Accordingly, there may be employed a simplemethod as such using two types or more of polymers belonging in animmiscible system, in which the surface of the polymer in charge of themechanism for supplying water to the interface is modified in such amanner to achieve good affinity with the other polymers, and the polymeris dispersed in microscopic level. As a matter of course, the presentinvention may be utilized more conveniently by employing a combinationof polymers in which there is no need of improving the affinity.

The ratio of the aggregate of the domain structure accounting in thesurface of the polishing pad, i.e., the surface density, differsdepending on the matrix. In case a polyamide resin or polyurethane resinhaving high water absorptivity is used, the usage thereof can be setsmall, but in case a polyacrylic resin such as polymethyl methacrylateor a polyimide is used, the ratio thereof must be set high. In general,the preferred ratio is in a range of from 5% to 50%, however, theoptimal value should be set properly depending on the combination of theresins. This process can be readily practiced by those in the art. Incase the surface density is set high, the resulting polishing pad tendsto yield weaker mechanical properties and becomes brittle, and it tendsto yield inferior polishing properties as to easily cause, for instance,dishing and erosion.

The shape of the hydrophilic polymer is preferably provided inparticles, non-woven, or textiles from the viewpoint of ease inhandling. The particles are preferably 500 μm or less in diameter, andmore preferably, those 100 μm or less in diameter are used. Those toolarge in diameter are not preferred, because they tend to cause frequentdrop out from the matrix. The fibers constituting the non-woven ortextiles may be hollow fibers, although there may be found difficultiesin controlling the intrusion of matrix inside the hollow portion.

The ratio of the hydrophilic polymer accounting in the surface of thepolishing pad, i.e., the surface density, differs depending on thematrix. In case a polyamide resin or polyurethane resin having highwater absorptivity is used, the usage thereof can be small, but in casea polyacrylic resin such as polymethyl methacrylate or a polyimide isused, the ratio thereof must be set high. In general, the preferredratio is in a range of from 5% to 50%, however, the optimal value shouldbe set properly depending on the combination of the resins. This processcan be readily practiced by those in the art. Again, in case the surfacedensity is set high, the resulting polishing pad tends to yield weakermechanical properties and becomes brittle, and it tends to yieldinferior polishing properties as to easily cause, for instance, dishingand erosion.

By mixing a hydrophilic organic material substantially insoluble towater, the wettability of the polishing pad surface can be improved, andalthough the detail of the mechanism is still unknown, dust adhesion canbe reduced. Accordingly, it is believed that the scratches can beminimized. The effect of suppressing dust adhesion can be obtained bymixing hydrophilic polymers at a mixing ratio of 1 to 70% by weight withrespect to the unit mass of the polishing pad. In case the mixing ratiois small, the effect is also small, and is greater for a larger mixingratio, but there often occurs a case of impairing the physicalproperties of the matrix. More specifically, the hardness of the matrixdecreases as to lower the bending strength, thereby leading to causebrittle fracture. Accordingly, the mixing ratio is preferably in a rangeof from 10 to 60% by weight, and more preferably, from 20 to 50% byweight. The particles and/or fibrous materials made of hydrophilicpolymer is substantially insoluble to water, they do not affect theproperties of the dispersion independent of whether or not thedispersion contains free polishing abrasives. Hence, favorable polishingcan be conducted. Thus, in contrast to the conventional polishing padsin which an increase in hardness and an improvement in dust adhesion orscratches were a tradeoff, the polishing pad of the invention itself canbe increased in hardness without generating dust adhesion or scratches.Hence, the flexural modulus of elasticity of the polishing pad can beconsiderably increased as compared with the polishing pads known in theart, and extremely favorable planarization characteristics can beachieved.

The term “substantially insoluble to water” signifies that thesolubility of the material for water at 25° C. is 1% or lower. The term“hydrophilic” is, basically, an expression of the property of a resinthat absorbs water inside the resin, and it does not signify that theresin contains water incorporated inside the resin in macroscopic level.More specifically, in case of evaluating hydrophilic properties, a testpiece immersed in water for 24 hours was taken out and placed in asealed vessel, and water was driven out from the test piece by applyingcentrifugal force of 1400 G to 1450 G for 30 seconds thereto to measurethe hygroscopic weight. The weight gain was obtained in accordance withequation 1 given below.Weight gain (%)=(Hygroscopic weight−dry weight)/dryweight×100  (equation 1)

The term “hydrophilic” as referred herein signifies a property of thematerial showing a weight gain of 2.0% or higher in case the material isimmersed to water at 50° C. for 24 hours. In the present invention, theweight gain is preferably 5.0% or higher. In case the value is too high,swelling occurs on the polishing pad during polishing as to impair thesurface planarity of the polishing pad, and this is not preferredbecause large fluctuation generates on the polishing rate. Furthermore,a high volume-swelling ratio is not preferred, because the strength ofthe polishing pad itself greatly degrades during polishing. Accordingly,it is preferred that the weight gain is 15% or lower, and in general,10% or lower is preferred.

More quantitatively, hydrophilic properties are expressed by nominalwater content. This represents the water content at a humidity of 65%and a temperature of 20° C., as shown by the following equation.Nominal water content (%)=(Hygroscopic weight−dry weight)/dryweight×100  (equation 2)

Then, water absorptivity refers to the water content measured 10 minutesafter immersing the article in water at 25° C., expressed as follows:Water absorptivity (%)=(Hygroscopic weight−dry weight)/dryweight×100  (equation 3)

It is preferred that the speed of absorbing water is high, and it ispreferred that a saturated state is achieved within 10 minutes. However,a resin that shows the change of 90% in 24 hours can be suitablyapplied. Still, in case particles and/or fibrous materials are used asthe hydrophilic material substantially insoluble to water, deformationof the pad itself occurs in case water absorptivity exceeds 5000%, orstress of th polishing plane becomes too large as to make the polishingpad unfeasible. Hence, the water absorptivity is preferably within3000%, and more preferably, within 2000%. In case of sheet-likematerials, fibrous materials having an aspect ratio of 5 or higherand/or granules formed from the composites thereof, the pad itselfundergoes deformation in case water absorptivity exceeds 1000%, or thestress of the polishing plane becomes too large as to make the padunfeasible. Hence, in such a case, the water absorptivity is preferablywithin 6000%, and more preferably, within 3000%.

In case of mixing particles and/or fibrous materials as the hydrophilicpolymer substantially insoluble to water, there may be used those havingnominal water content of about 1%, but preferably used are those havingnominal water content of 3% or higher. To further suppress dustadhesion, preferred to use are those having nominal water content of 5%or higher, and those of 7% or higher are more preferred because they canreduce the mixing ratio of the particles and/or fibrous materials. Theterm “particles” refer to those basically spherical in shape, but thosedeformed or having irregularities may also be used. Such havingirregular and complex shape as the so-called fumed silica can befavorably used. Fibrous materials in this case refer to those having anelongated shape, with a ratio of the major axis to the minor axisexceeding 3.

The diameter of the particles (which refers to the maximum diameter incase the shape is not a sphere) is preferably 500 μm or less, and morepreferably, 100 μm or less. Too large a diameter is not preferred,because the particles tend to cause frequent drop out from the matrix asto increase dust generation, thereby leading to impaired durability as apolishing pad. Accordingly, those having a diameter in a range of from 1to 50 μm are most preferably used. The fibrous materials may be hollowfibers. The cross section shape may be of any shape proposed for newsynthetic fibers, such as circular, ellipsoidal, star-like, and thelike.

The ratio of the particles and/or fibrous material made of substantiallyinsoluble to water accounting in the surface of the polishing pad, i.e.,the surface density, differs depending on the matrix used. In case apolyamide resin or polyurethane resin having high water absorptivity isused, the usage thereof can be set small, but in case a polyacrylicresin such as polymethyl methacrylate or a polyimide is used, the ratiothereof must be set high. The surface density can be obtained byobserving under optical microscope and by then performing imageprocessing. In general, the preferred ratio is in a range of from 5% to80%, however, the optimal value should be set properly depending on thecombination of the resins. This process can be readily practiced bythose in the art. Again, in case the surface density is set high, theresulting polishing pad tends to yield weaker mechanical properties andbecomes brittle, and it tends to yield inferior polishing properties asto easily cause, for instance, dishing and erosion.

The mixing ratio of the particles and/or fibrous material depends on thenominal water content and water absorptivity referred above, butbasically, the mixing ratio can be set lower in case nominal watercontent the water absorptivity is high, and it should be set higher incase the water absorptivity is low. In case the mixing ratio is lessthan 4%, the effect is insufficiently exhibited, but with a mixing ratioof 4% or higher, the dust adhesion and scratch flaws can be decreased. Alower mixing ratio results in a lower effect, and although a higherratio results in a higher effect, the physical properties of the pad arefrequently impaired. More specifically, the hardness of the paddecreases as to lower the bending strength, thereby leading to causebrittle fracture. Accordingly, the mixing ratio is preferably in a rangeof from 7 to 60% by weight, and more preferably, from 20 to 50% byweight.

In case of mixing sheet-like hydrophilic materials substantiallyinsoluble to water, those having nominal water content of from about 1%can be used, but preferably used are those having a water content of 3%or higher. To further suppress dust adhesion, those having a watercontent of 5% or higher are preferred, and those of 7% or higher aremore preferred because they can reduce the mixing ratio of the particlesand/or fibrous material.

The mixing ratio of the sheet-like hydrophilic materials substantiallyinsoluble to water depends on the nominal water content and waterabsorptivity referred above, but basically, the mixing ratio can be setlower in case nominal water content the water absorptivity is high, andit should be set higher in case the water absorptivity is low. In casethe mixing ratio is less than 3%, the effect is insufficientlyexhibited, but with a mixing ratio of 3% or higher, the dust adhesionand scratches can be decreased. A lower mixing ratio results in a lowereffect, and although a higher ratio results in a higher effect, thephysical properties of the pad are frequently impaired. Morespecifically, the hardness of the pad decreases as to lower the bendingstrength, thereby leading to cause brittle fracture. Accordingly, themixing ratio is preferably in a range of from 5 to 60% by weight, andmore preferably, from 20 to 50% by weight. In case of a sheet-likematerial, in particular, it can be mixed up to about 85% by weightbecause fracture less occurs on a sheet-like material.

A sheet-like hydrophilic material substantially insoluble to watercomprises at least one of non-woven-like, textile-like, woven-like,felt-like, porous membrane-like, sponge-like, and film-like sheet. Anon-woven-like sheet refers to a cloth in wider definition in which thefibers are confounded, but it may be stressed or may containirregularities. Non-woven-like, woven-like, textile-like, and felt-likesheets are obtained from fibrous materials. Fibrous materials in thiscase refer to those having an elongated shape, with a ratio of the majoraxis to the minor axis exceeding 10. In wider definition, porousmembrane-like and sponge-like sheets signify films containingtwo-dimensional and/or three-dimensional open pores with high porosity,and film-like sheets refer to those substantially free from open pores.

The diameter (which refers to the maximum diameter in case the shape isnot a sphere) of the fibers constituting the above materials ispreferably 100 μm or less, more preferably, 50 μm or less, and suitablyused are those having a diameter in a range of from about 2 to about 20μm. In case of ultrafine fibers, known are those having a diameter ofless than 2 μm, and it is convenient to use such. Those too large indiameter are not preferred, because they tend to cause frequent drop outfrom the matrix and reduce the durability of the polishing pad. Thefibrous materials may be hollow fibers. The cross section shape may beof any shape proposed for new synthetic fibers, such as circular,ellipsoidal, star-like, and the like. The porous membrane-like andsponge-like sheets contain pores connected with fine columns, and thediameter of the columns range from about 10 nm to about 1 mm; however,there is no particular limits concerning their size. By using sheetshaving interstices accounting in volume, i.e., porosity, of a high ratioexceeding 25%, and by shaping them by compressing in the thicknessdirection, the fluctuation in the thickness direction can be favorablysuppressed. The film-like sheets are suitably used for forming thelayers (separation layer) that separate the layers constituting thelaminate from each other. In particular, ultra thin films having athickness of less than 1 μm can be used in a manner similar to thenon-woven-like, woven-like, textile-like, felt-like, porousmembrane-like, and sponge-like sheets.

The mixing ratio of the particles formed from fibrous hydrophilicmaterials with an aspect ratio of 5 or higher and substantiallyinsoluble to water and/or the composite thereof depends nominal watercontent and water absorptivity referred above, but basically, the mixingratio can be set lower in case the nominal water content and the waterabsorptivity is high, and it should be set higher in case the waterabsorptivity is low. In case the mixing ratio is less than 4%, theeffect is insufficiently exhibited, but with a mixing ratio of 4% orhigher, the dust adhesion and scratches can be decreased. A lower mixingratio results in a lower effect, and although a higher ratio results ina higher effect, the physical properties of the pad are frequentlyimpaired. More specifically, the hardness of the pad decreases as tolower the bending strength, thereby leading to cause brittle fracture.Accordingly, the mixing ratio is preferably in a range of from 7 to 60%by weight, and more preferably, from 20 to 50% by weight. The aspectratio is expressed by (the length of the major axis of theparticle)/(the length of the minor axis of the particle), and in thepresent invention, those having an aspect ratio of 5 or higher isreferred to as fibrous materials. A fibrous composite refers to acomposite formed by aggregating those fibrous materials in theirfibrillation state. For instance, it refers to a shape of an ultrafinefiber precursor having a core and sheath structure. In the presentinvention, particles refer to the fibrous materials aggregated into aparticle-like shape. The aspect ratio is defined for the ultrafinefibers constituting the particle-like material. By mixing the materialsabove with such a shape as fillers, the polishing pad itself allowsstress relaxation during polishing as to suppress the generation of dustadhesion and scratches.

In case of a polishing pad comprising an organic polymer matrix obtainedby laminating the sheet-like materials, in particular, plural sheet-likematerials are laminated to form a single polishing pad. Accordingly, thepolishing pad of the present invention yields an extremely high strengthagainst bending, and rarely causes fracture. As a matter of course, thepolishing pad may be constructed by using a single thick sheet-likematerial. However, a polishing pad having high stability in polishingproperties and yet capable of precisely controlling the state of thepolishing plane can be readily formed by forming layers having athickness of about 1 μm and/or thicker per layer, and by thensuperposing a plurality of such layers. In general, those having athickness of 5 μm or more are used, and preferably, those with athickness of 100 to 300 μm are used. The thickness or the material ofthe layers need not be the same, and the resin content and/or type ofthe matrix resin as well as the thickness and/or type of the sheet-likematerials may be differed every layer to realize precisely designedpolishing pad.

For instance, a cushion layer comprising foamed polyurethane, rubbersheet, and the like, may be combined with a polishing layer portion,cushion layer portion, and the separating layer portion to make one set,and a plurality of such sets may be laminated. By once adhering such apad to a polishing disk, a long-life polishing pad, which allows use ofthe pads without exchanging for a long term never realized before can beprovided. The incorporation of a separating layer allows polishing to beperformed with a virgin plane formed by dressing without allowing thepolishing layer to be brought into contact with the polishing liquid orwith the polishing dispersion intruded from the polishing plane. Hence,an extremely high polishing stability can be realized. Furthermore, incase it is necessary to provide layers for polishing alternately aninterlayer insulator film and a metal, it is possible to shape the padwith optimal arrangement; for instance, an extremely hard layer may beprovided for polishing the interlayer insulator film, and a soft layermay be provided for metal polishing. Those in the art may easilydetermine such a combination. In this manner, the present inventionallows improvement in production through put, and is effective for totalcost down.

As the method for forming the laminated polishing pad, there can be useda method comprising forming in advance a compound of a sheet-likehydrophilic material substantially insoluble to water with an organicpolymer matrix, optionally, together with inorganic fine particlesand/or water soluble material, and after impregnating, shaping theresulting compound by thermal compression. In such a case, the viscosityof the compound may be adjusted by using a solvent, and thermalcompression for shaping may be applied after drying. Since a sheet-likematerial is used, the matrix resin alone may be impregnated underpressure, and a layer formed by uniformly dispersing inorganic particlesand/or by uniformly scattering water-soluble substance in a similarmanner may be laminated thereafter to subject the resulting laminatedstructure to thermal compression shaping. By increasing the number oflayers, the fluctuation in physical properties of the resultingpolishing pad can be reduced.

It is also possible to polymerize the monomer molecules of the matrix ofa sheet-like hydrophilic material substantially insoluble to water withthem, optionally, after impregnating them with inorganic fine particlesand/or water-soluble materials. In case the matrix is of a two-part typesuch as polyurethane, the sheet-like material may be impregnated underpressure after mixing the base agent or the hardening agent, and thenshaped. Cutting process may be applied thereafter to finish into theshape of the polishing pad. The details depend on the miscibility ofeach of the matrices with the hydrophilic polymer substantiallyinsoluble to water, as well as on the individual physical propertiessuch as the heat resistance, polymerization characteristics, meltviscosity, and the like.

As the method for shaping a mixture of particles, and/or fibrousmaterials, and/or fibrous materials having an aspect ratio of 5 orhigher, and/or particles formed from the composites thereof into apolishing pad, there can be mentioned a method comprising forming inbeforehand a compound of the matrix with the hydrophilic polymersubstantially insoluble to water, and then shaping the resultingcompound by thermal compression. Otherwise, there may be used meltextrusion molding. Also available is a method such as using an injectionpress.

It is also possible to polymerize the monomer molecules of the matrixafter impregnating a hydrophilic polymer substantially insoluble towater with them. In case the matrix is of a two-part type such aspolyurethane, the base agent or the hardening agent is mixed with ahydrophilic polymer substantially insoluble to water in beforehand, andafter further mixing therein the hardening agent or the base agent,respectively, the resulting mixture is fed inside a proper mold afterdegassing operation. It is also possible to apply cutting processthereafter to finish the resulting product into the shape of thepolishing pad. The details depend on the miscibility of each of thematrices with the hydrophilic polymer substantially insoluble to water,as well as on the individual physical properties such as the heatresistance, polymerization characteristics, melt viscosity, and thelike. However, the combination can be readily selected by those in theart. Thus, concerning the method of production, the polishing padaccording to the present invention can be obtained by combining knowntechniques.

The polishing pad of the invention preferably comprises grooves or holesprovided on its surface with an aim to accelerate supplying ordischarging polishing liquid to or from the polishing plane. The groovesmay be provided in various configurations, such as concentric circles,spirals, radiating lines, checker board arrangement, and the like. Thegrooves may have cross section shapes in the form of a rectangle,triangle, semicircle, and the like. The grooves are provided at a depthof from 0.1 mm to the thickness of the polishing layer, at a widthranging from 0.1 to 5 mm, and at a pitch ranging from 2 to 100 mm. Theholes may or may not penetrate the polishing layer. The diameter of theholes may be selected in a range of from 0.2 to 5 mm. The pitch of theholes may range from 2 to 100 mm.

As the resin or the organic polymer matrix constituting the polishingpad, usable are the thermoplastic resins such as those based onpolyamide, polyacrylic, polyolefins, polyvinyl, ionomers, polycarbonate,polyacetal, polyurethane, polyimide, and the like. Also usable are thederivatives, copolymers, and graft products of those enumerated above. Amixture of those is also usable, but the blending ratio must be set assuch to result in a desired hardness.

For instance, the hardness may be improved effectively by mixinginorganic fine particles. The technology disclosed in relation tonanocomposites may be applied and extended. More specifically, usable asinorganic fine particles are the crystals of, for instance, silica,ceria, alumina, zirconia, titanium, tungsten, barium carbonate, bariumsulfate, carbon black, clay minerals such as montmorillonite, zeolite,and the like. Mixtures thereof are also usable. It is also possible tosubject the surface to modification treatment to improve their affinitywith the matrix.

The usable particle diameter is in a range of from about 3 nm to about50 μm, but too large a particle size increases the danger of causingscratches. Accordingly, preferably, the particle diameter is 20 μm orsmaller, and more preferably, 5 μm or smaller. Concerning the weightratio of mixing the fine particles of silica, ceria, alumina, zirconia,titanium, tungsten, barium carbonate, barium sulfate, carbon black, clayminerals such as montmorillonite, zeolite, and the like, an effect canbe obtained at an addition of from about 1% to about 80%. In case thefine particles are added to a high concentration, they are effective notonly for increasing the hardness of the polishing pad, but also for apolishing pad inclusive of abrasives, i.e., as a so-called polishing padwith fixed abrasives. In such a case, the effect is smaller with smallerparticle diameter; hence, particles with diameter of 30 nm or greaterare preferred, and from the viewpoint of increasing the polishing rate,more preferred are particles 100 nm or greater in diameter. By changingthe particle diameter and the mixing ratio of such fine particles, therecan be obtained polishing pads corresponding to the properties of thearticle to be polished.

As other usable organic polymer matrices, there can be mentionedthermosetting resins such as those based on polyurethane, epoxy,phenolic, melamine, urea, polyimide, and the like. Mixed resins(inclusive of alloys), as well as the modification techniques such ascopolymerization, grafting, modification, and the like, may be employed.In the present invention, the resin constituting the polishing pad isproperly selected based on the desired hardness, elasticity, and wearresistance. In this case again, inorganic fine particles may be mixed ina manner similar to the case of using a thermoplastic resin as describedabove. In this case, however, the particles should be dispersed in thestate of a prepreg.

Since a thermoplastic resin is softer than a common thermosetting resin,particles and/or fibrous materials made of a hydrophilic organicmaterial substantially insoluble to water that are mixed with thethermoplastic resin may be lower in nominal water content. Those havinga nominal water content as low as about 1% may be used, but to furtherdecrease the dust adhesion and scratches, those having a water contentof 3% or higher are preferred. Similarly, the thermosetting resins usedare preferably high in nominal water content. In such a case, inparticular, the water content is preferably 5% or higher, and morepreferably, 7% or higher.

The polishing pad according to the present invention after shapingpreferably yields D hardness value exceeding 65. In case D hardness is65 or lower, the polishing pad becomes too soft as to cause dishing anderosion, and this is not preferred. Furthermore, to increase thepolishing rate, the polishing pad preferably yields a D value of 70 orhigher, and more preferably, 80 or higher. In the present invention,those with a further increased D hardness exceeding 90 are also usablewithout causing any problems concerning scratches and dust adhesion.Accordingly, favorable polished planarization characteristics neverachieved to present can be exhibited by the present invention.

As explained above, the flexural modulus of elasticity of the polishingpad can be increased as compared with a conventional polishing pad. Toachieve favorable planarization characteristics, the flexural modulus ofelasticity is preferably 0.5 GPa or higher, and more preferably, 2 GPaor higher. Since there is no problems of dust adhesion and scratches,further higher flexural modulus of elasticity of 5 GPa or higher but nothigher than 20 GPa is preferred for the polishing pad according to thepresent invention. However, since too high a flexural modulus ofelasticity makes the attachment of the polishing pad difficult, thepreferred range is 100 GPa or lower.

With respect to the hydrophilic polymers substantially insoluble towater, for instance, there can be used resins based on cellulose,acrylic acid, polyamide, starch, and the like, as well as thecrosslinked products and polymers containing those resins as theprincipal component. Commercially available polyvinyl pyrrolidone,polyvinyl pyrrolidone/vinyl imidazole copolymers, high water absorptionresins, pulp, paper, cellulose esters, aramid resins such as “Kevlar”,cellulose imparted with various types of charges for use as ion exchangeresins, and the like may well be used. The surface of such resins may besubjected to modification treatment to improve the affinity with thematrix. Basically, those having a solubility parameter δ_(sp) of 11.5 orhigher and δ_(h) of 4 or higher are favorably used. For the solubilityparameter, reference can be made to, for instance, Takeshi Matsuura,“Gosei-maku no Kiso (Fundamentals of Synthetic Films)” (published byKitami Shobo, Oct. 20, 1985), pages 32 and 33.

For the polymers substantially insoluble to water used in the polishingpad according to the present invention, there may also be used resinsbased on starch, polysaccharides such as chitin, protein, polyamide,polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and the like, aswell as the crosslinked products and copolymers containing those resinsas the principal component thereof. Commercially available naturalfibers such as silk, wool, cotton, linen, and the like may beeffectively utilized. Furthermore, resins that are inherentlyhydrophobic but into which groups such as sulfonic group, amino group,carboxyl group, hydroxyl group, and the like are introduced may well beused. Hydrophobic resins in this case refer to those having a weightgain with reference to equation 2 above of less than 2%. Furtherpreferred is to use those in which sodium ion content is suppressed to400 ppm or lower. The sodium ion content is suppressed to, morepreferably, 50 ppm or lower, and further preferably, 10 ppm or lower.

The polishing pad according to the present invention may further containwater-soluble materials. Commercially available polymers include varioustypes of polyalkylene glycols, polyvinyl alcohol, polyvinyl acetate,chitosan, polyvinylpyrrolidone, polyvinyl imidazole, water-solublepolysaccharaides, and the like, and these may be used. In addition tothose, various types of low molecular substances such as various typesof inorganic salts may be mixed. By mixing the matrix with thewater-soluble polymers in this manner, the water-soluble polymer portiondissolves and drops out from the matrix during polishing as to formmicro-sized hetero fine pores. In this case again, a compound formed inadvance may be shaped by thermal compression, or subjected to meltextrusion molding. Also available is a method such as using an injectionpress, and combinations of known techniques may be employed. It is alsopossible to use hydrophilic polymers substantially in soluble to watertogether with water-soluble polymers. Since particles and/or fibrousmaterials made of hydrophilic organic materials substantially insolubleto water, i.e., hydrophilic organic materials, are used in the presentinvention, these are dried on shaping a polishing pad according to thepresent invention. However, vapor generates on heating for shapingbecause complete removal of water is difficult. Accordingly, intersticescan be formed at portions other than particles and/or fibrous materials.In case thermosetting resins are used, water generates in some casessuch as those in which phenolic resin is employed. Thus, by using suchresins, interstices can be formed at portions other than particlesand/or fibrous materials. To control the size of the interstices, forinstance, water vapor may be properly drawn out during setting. However,when necessary, water-soluble materials may be mixed in small quantitiesto enable precise control of the interstices. Furthermore, since thewater-soluble materials elute out during polishing, interstices can beformed only on the surface of the polishing pad. Such intersticesimprove the retention of the free abrasives contained in the polishingslurry, or are effective for the removal of polish wastes, and in somecases, they are advantageous in increasing the polishing rate. Moreover,in case the water-soluble materials dissolve in the dispersion of thepolishing liquid, the viscosity of the dispersion can be changed.Accordingly, in case xanthane rubber, i.e., a water-solublepolysaccharide, for instance, is mixed and dissolved in the polishingliquid, the solution tends to exhibit Bingham fluid-likecharacteristics; hence, probably, on the semiconductor wafer havingsurface irregularities, the diffusion of abrasive grains at the concaveportions is suppressed. In this manner, it works effective for improvingthe planarity, particularly, the global planarity on polishing thewafer. Although it is possible to exhibit the effect of thewater-soluble materials with an addition of about 0.01 wt % with respectto the unit weight of the polishing pad, the water-soluble materials arepreferably added at an amount of 0.5 wt % or higher but not higher than5 wt % to effectively achieve these effects. In case the water-solublematerials are added at an amount exceeding 10 wt %, the characteristicsof the polishing dispersion change unfavorably excessively. Although itis possible to increase the addition amount by using a lower molecularweight substance which less influences the viscosity of the dispersion,this is not practical from the viewpoint of increasing cost.

The polishing pad according to the present invention may containnanocomposites above such as inorganic particles, and easilyaccomplishes improved polishing properties by enabling harder polishingpads as compared with a conventionally known polishing pads made fromresins. More specifically, the generation of dishing and erosion can bereduced. In particular, favorable results concerning scratches can beobtained by combining them with abrasive grains having smaller particlediameter.

Furthermore, the polishing pad according to the present invention ischaracterized in one aspect that the nanocomposite used therein is ananocomposite with silica particles, and that the polishing pad isusable as a fixed abrasive pad in which polishing liquid free fromabrasives is supplied. The term “nanocomposite” as expressed in thepresent invention refers to materials ranging from a mixture ofparticles in the order of nanometer size to a mixture comprising fineparticles about several tens of micrometers in size. In case theparticles are too large, the effect of increasing hardness becomessmall. Hence, the diameter of the particles is preferably 20 μm orsmaller, and in order to reduce the danger of generating scratchesduring polishing, preferably used are particles 1 μm or smaller indiameter. On the contrary, in case particles too small in diameter areused, they no longer exhibit the effect as fixed abrasives. Hence,preferred are particles 10 nm or larger in diameter. As theorganic-inorganic nanocomposites, preferably used is at least oneselected from a combination of a phenolic resin and silica particles, acombination of an epoxy resin and silica particles, and a combination ofa polyamide resin and silica particles. However, any nanocomposite newlydeveloped may be used in addition to those enumerated above. Forinstance, ceria based fine particles are a candidate.

Concerning the quantity of mixing silica fine particles as thenanocomposite in % by weight, the effect can be achieved even with anamount of about 1%, and the amount may be increased up to about 80%. Thesilica particles maybe mixed in an amount of, in % by weight, 2 to 70%in case of polyamide resin, 2 to 85% in case of epoxy based resin, and 2to 50% in case of phenolic resin. The addition of the nanocomposite canbe set properly depending on the desired hardness. Furthermore, thosecommercially available may be used.

In addition to above, semiconductor wafers can be polished by using fineparticles of barium carbonate. Fine particles of barium carbonate may beused in combination with a hydrophilic polymer, or may be used alone.

More specifically, usable as inorganic fine particles are the crystalsof, for instance, silica, ceria, alumina, zirconia, titanium, tungsten,barium carbonate, barium sulfate, carbon black, clay minerals such asmontmorillonite, zeolite, and the like. Mixtures thereof are alsousable. It is also possible to subject the surface to modificationtreatment to improve their affinity with the matrix.

The usable particle diameter is in a range of from about 3 nm to about50 μm, but too large a particle size increases the danger of causingscratches. Accordingly, preferably, the particle diameter is 20 μm orsmaller, and more preferably, 5 μm or smaller. Concerning the weightratio of mixing the fine particles of silica, ceria, alumina, zirconia,titanium, tungsten, barium carbonate, barium sulfate, carbon black, clayminerals such as montmorillonite, zeolite, and the like, an effect canbe obtained at an addition of from about 1% to about 80%. In case thefine particles are added to a high concentration, they are effective notonly for increasing the hardness of the polishing pad, but also for apolishing pad inclusive of abrasives, i.e., as a so-called polishing padwith fixed abrasives. In such a case, the effect is smaller with smallerparticle diameter; hence, particles with diameter of 30 nm or greaterare preferred, and from the viewpoint of increasing the polishing rate,more preferred are particles 100 nm or greater in diameter. By changingthe particle diameter and the mixing ratio of such fine particles, therecan be obtained polishing pads corresponding to the properties of thearticle to be polished.

The polishing pad according to the present invention is characterized inthat, on taking the centerline average roughness Ra of a single siliconwafer having provided with an oxide film after polishing, the differencein value of Ra falls in a range of 0.2 μm or less with respect to thesurface roughness profile generated by dressing before polishing takenas the standard. For instance, it is characterized in that it comprisesat least two types of domains formed by blending at least two types ormore of polymers differing in abrasive wear rate on polishing. Manytypes of polymers undergo microscopic phase separation, and varioustypes of combinations are known. Hence, such knowledge can be utilized.However, care should be taken since the domain size tends to be toosmall. The resins to be used are preferably combined in such a mannerthat they may exhibit poor miscibility with each other, or that onebecome a liquid while the other does not on shaping.

The size of the two types or more of domains is ideally the same forboth, and the ratio of the average total domain area (i.e., the totalarea of the smallest domain/the total area of the largest domain) ispreferably in a range of from 0.1 to 3.5. Furthermore, a ratio in arange of from 0.3 to 2.5 is more preferred because the difference inpolishing rate is small. However, in case three types or more domainsare formed, and in case two of them are in an included relation, theyare regarded as two types of domains present. The size of the domainscan be measured with an optical microscope. Commercially available areapparatuses comprising a combination of an optical microscope and CCDcamera. By utilizing such apparatuses, data processing can be easilyperformed on a personal computer and the like. Preferably, at least oneof the formed domains has a size ranging from 10⁻¹² m² to 10⁻⁶ m². Thesize of a single domain is larger the better. However, in case it is toolarge for a polishing pad, the mechanical strength of the pad surfacetends to be too low, and may lead to an extremely impaired durabilitywhen used in polishing. In such a case, the problem of making it unableto obtain a sufficiently high polishing rate may arise. The thresholdvalue for the size differs depending on the resin mainly constitutingthe pad, however, it has been found that this disadvantage can becircumvented by setting the diameter to 1 mm or smaller. The polishingcharacteristics are not particularly affected by whether the domain sizeis large or small; however, it leads to difficulties concerningshapability of the polishing pad and the suppression of the fluctuationin quality. It is one solution to establish a so-called micro phaseseparation structure, but it is difficult to maintain the same state forthe surface and the inside of the polishing pad, and hence, it isextremely difficult to control the micro phase separation structure overthe entire film thickness. Accordingly, there may be employed a simplemethod as such using two types or more of polymers belonging in animmiscible system, modifying the surface of one polymer in such a mannerto achieve good affinity with the other polymers, and then dispersingthe polymer in microscopic level. As a matter of course, the presentinvention may be utilized more conveniently by employing a combinationof polymers in which there is no need of improving the affinity.

The polishing pad designed in the manner above realizes a polishing padcapable of maintaining favorable polishing characteristics, forinstance, even in case of polishing a semiconductor wafer, there is noneed of performing dressing using a diamond dresser, and yet, favorablepolishing characteristics can be continuously obtained by carrying outsimple operation of brushing and the like without applying any load.Although the mechanism is yet to be clarified, the use of differenttypes of polymers in mixture probably provides domains that individuallyundergo abrasive wear at different rates, thereby resulting in auniformly maintained surface roughness.

On studying the polishing rate in practice, no fluctuation in polishingrate was found even in case five semiconductor wafers were continuouslypolished. Furthermore, the surface roughness was measured at the sametime to find little change in the value of the centerline averageroughness Ra. In this case, it should be stressed that the value of thecenterline average roughness, Ra, generally fell in a range of from 3 to5 μm, and the change on polishing was 0.2 μm/wafer or lower.Furthermore, a change in Ra of 0.15 μm/wafer or lower is preferred fromthe viewpoint of increasing stability in polishing rate. In case furtherprecision is required, the change in Ra of 0.1 μm/wafer or lower ispreferred. By thus incorporating a mechanism for suppressing the changein the value of the centerline average roughness Ra small as in thepresent invention, it has been found that the polishing characteristicscan be maintained, and that the objects can be achieved.

Furthermore, the change in value of the surface centerline averageroughness Ra was found to be further minimized by mixing a water-solublepolymer in the matrix, since the water-soluble polymer portion dissolvesand falls out from the matrix during polishing. It is possible to use ahydrophilic polymer insoluble to water together with a water-solublepolymer.

By employing the constitution above, a polishing pad having favorableglobal planarization characteristics and yet superior in polishingstability can be provided while suppressing the generation of problemsof dust adhesion and scratches. There may slightly remain problems ofdust adhesion and scratches depending on the combination and/or themixing weight ratio of the matrix resin and the hydrophilic polymersubstantially insoluble to water. In such a case, optimization can becarried out by measuring the water absorptivity or the water absorptionrate of the finished resin sheet, and by then performing adjustments asfollows. Concerning absorptivity, a value of 0.8% or higher for one-hourabsorptivity is preferred, and to suppress dust adhesion, a value of 1%or higher is preferred, more preferably, 2% or higher. Too high anabsorptivity is not preferred because the stability in polishing ratebecomes impaired. Hence, the absorptivity is preferably 15% or lower.Concerning absorption rate, it is preferred that the water absorptionrate within 5 minutes from contact with water is 3%/hr or higher, and tofurther suppress the problems of dust adhesion and scratches fromoccurring, the rate is preferably 6%/hr or higher, and more effectively,it is preferably 9%/hr or higher.

Preferably, the polishing pad comprises grooves or holes provided on itssurface with an aim to accelerate supplying or discharging polishingliquid to or from the polishing plane. The grooves may be provided invarious configurations, such as concentric circles, spirals, radiatinglines, checker board arrangement, and the like. The grooves may havecross section shapes in the form of a rectangle, triangle, semicircle,and the like. The grooves are provided at a depth of from 0.1 mm to thethickness of the polishing layer, at a width ranging from 0.1 to 5 mm,and at a pitch ranging from 2 to 100 mm. The holes may or may notpenetrate the polishing layer. The diameter of the holes may be selectedin a range of from 0.2 to 5 mm. The pitch of the holes may range from 2to 100 mm. Any configurations and shapes may be selected so long as theysatisfy the requirements of suitably supplying the polishing liquid tothe polishing plane, of increasing retention of the polishing liquid, offavorably discharging and/or accelerating the discharging of thepolishing liquid together with the polishing waste. The polishing padmay be processed into various shapes, such as those of disks, donuts,belts, and the like. The thickness of the polishing pad may vary fromabout 0.1 mm to about 50 mm, or may be provided thicker than those.Concerning the diameter when shaped into disks or donuts, the diametermay range from ⅕ to 5 times as large as that of the size of the articleto be polished; however, those too large in size are not preferredbecause the processing efficiency becomes impaired.

The polishing pad obtained in accordance with the present invention maybe used as a composite polishing pad by laminating it with a cushionsheet having a cushioning function. A semiconductor substrate comprisesa larger waviness in addition to local irregularities, and in manycases, a cushion sheet is frequently provided under the hard polishingpad (on the polishing disk side) as a layer absorbing such waviness. Asthe cushion sheet, a foamed urethane based material and a rubber-basedmaterial may be used in combination.

There is no particular limitations on the material to be employed forthe cushion sheet, and, in addition to the commonly used polyurethaneimpregnated non-woven cloth (for instance, Suba400 (trademark)manufactured by Rodel Inc.), there may be employed rubber, foamedelastomer, foamed plastics, and the like. However, preferred is acushion layer having a volume elastic modulus of 60 MPa or higher andhaving a tensile modulus of elasticity in a range of from 0.1 to 20 MPa.In case the tensile modulus of elasticity is small, there is a tendencyof impairing the uniformity in planarity of the entire surface of thesemiconductor substrate. Those having a high tensile modulus ofelasticity also tend to impair the uniformity in planarity of the entiresurface of the semiconductor substrate. Further preferable range for thetensile modulus of elasticity is from 0.5 to 10 MPa.

The volume elastic modulus as referred herein can be obtained byapplying an isotropic pressure to an article having its volume measuredin advance, and by measuring the change in volume. The volume elasticmodulus is defined as follows: Volume elastic modulus=appliedpressure/(change in volume/original volume). For instance, in case achange in volume of 0.00005 cm³ is obtained when a pressure of 0.07 MPais applied to an article having an original volume of 1 cm³, the volumeelastic modulus is 1400 MPa. As a method for measuring the volumeelastic modulus, there can be mentioned, for example, a methodcomprising measuring the volume of the article in advance, immersing thearticle in water contained in a vessel, placing the vessel in a pressurevessel and applying pressure thereto, and obtaining the change in volumeand the applied pressure from the change in height of water inside thevessel. Concerning the liquid into which the article is immersed, thereare no particular limitations so long as a liquid is used, butpreferably avoided is to use a liquid which swells or destroys thearticle; for instance, usable are water, mercury, silicone oil, and thelike. The tensile modulus of elasticity can be obtained by shaping thecushion layer into a dumbbell-like shape, applying tension thereto, andmeasuring the tensile stress while the tensile strain (=change intensile length/original length) is in a range of from 0.01 to 0.03.Thus, the tensile modulus of elasticity can be defined as follows:Tensile modulus of elasticity=((Tensile stress at a tensile strain of0.03)−(tensile stress at a tensile strain of 0.01))/0.02.

As a component constituting the cushion layer having the characteristicsabove, mentioned as non-limiting materials are rubbers, morespecifically, non-foamed elastomers such as natural rubber, nitrilerubber, neoprene rubber, polybutadiene rubber, polyurethane rubber,silicone rubber, and the like. The cushion layer is preferably providedat a thickness in a range of from 0.1 to 100 mm. In case the thicknessis too small, there is a tendency of impairing the uniformity inplanarity of the entire surface of the semiconductor substrate. On thecontrary, in case the thickness is too large, there is a tendency ofimpairing the local planarity. A further preferred range in thickness isfrom 0.2 to 5 mm. A still preferred range in thickness is from 0.5 to 2mm.

The polishing pad according to the present invention is used by fixingit to a polishing disk. In such a case, care should be taken that thecushion layer is fixed in such a manner that it may not be displacedduring polishing, and that the polishing layer may not be displaced fromthe cushion layer. As a method for fixing the cushion layer to thepolishing disk, there can be mentioned, without any limitations, amethod comprising fixing the cushion layer with a double-sided adhesivetape, a method comprising fixing with an adhesive, a method comprisingfixing the cushion layer by sucking it from the polishing disk, and thelike. As a method for fixing the polishing layer to the cushion layer,there can be mentioned, without any limitations, a method comprisingfixing the cushion layer with a double-sided adhesive tape or a methodcomprising fixing with an adhesive.

As the double-sided adhesive tape or an adhesive layer preferred foradhering the polishing layer to the cushion layer, there can bespecifically mentioned a double-sided adhesive tape 463, 465, 9204, andthe like manufactured by Sumitomo 3M Co., Ltd., a double-sided adhesivetape No. 591 and the like manufactured by Nitto Denko Co., Ltd., whichis a substrate-free acrylic adhesive transfer tape, Y-4913 and the likemanufactured by Sumitomo 3M Co., Ltd., which is a double-sided adhesivetape using foamed sheet as the base, and 447DL and the like manufacturedby Sumitomo 3M Co., Ltd., which is a double-sided adhesive tape usingsoft vinyl chloride as the base.

In case there is necessity of exchanging the polishing layer afterpolishing due to reasons such as inability of achieving the desiredpolishing rate and the like, in the present invention, it is possible todetach the polishing layer from the cushion layer while maintaining thecushion layer fixed to the polishing platen. Since the cushion layer hasa higher durability as compared with the polishing layer, it ispreferred to exchange the polishing layer alone from the viewpoint ofcost.

In case the polishing pad according to the present invention is used inthe production of semiconductor chips, for instance, it may be employedfor polishing a semiconductor wafer (bare wafer, and/or a wafer having asurface provided with an oxide film) before performing surfaceroughening process thereto, such that the fine irregularities inherentto the wafer, i.e., surface defects expressed as waviness ornanotopology, may be preferably removed. Then, surface-patterningprocess is performed by means of lithography and the like, and CMP isapplied thereafter. By carrying out the process steps using thepolishing apparatus according to the present invention, processing athigh planarity can be realized, and this easily satisfies therequirements of multilayering, high integration, and fineinterconnection of semiconductor chips. Furthermore, preferably used asthe polishing pad according to the present invention are those whosesodium ion concentration is suppressed to 400 ppm or lower; morepreferably, sodium concentration thereof is suppressed to 50 ppm orlower, and most preferably, 10 ppm or lower.

The polishing pad according to the present invention is utilized forpolishing the surface of insulating layers or metallic layers formed ona semiconductor wafer. As the insulating layers, there can be mentionedinterlayer dielectric films for metallic interconnections, a lowerdielectric film for metallic interconnections, and shallow trenchisolation for use in isolating elements. As metallic interconnections,examples include those of aluminum, tungsten, copper, and the like,which may be used in structures such as damascene, dual damascene, plug,and the like. In case copper is used for the metallic interconnection,barrier metals such as silicon nitride are also the objects to bepolished. Silicon oxide is mainly used for the dielectric film, however,by taking the problems concerning delay time into consideration, lowdielectric insulating films would also be brought into use. Although lowdielectric insulating film is softer and more brittle than siliconoxide, the polishing pad according to the present invention enablespolishing in a state relatively free from scratches. In addition tosemiconductor wafers, the polishing pad according to the presentinvention is also applicable to the polishing of magnetic heads, harddisks, liquid crystal displays, plasma display related members,sapphire, and the like.

The present invention is explained in further detail below by makingreference to some examples.

EXAMPLE

(Measurement of the Amount of Dust Adhered)

A polishing pad 1.2 mm in thickness and 38 cm in diameter was produced,and the surface thereof was subjected to a so-called X-Y grooveprocessing (processing of lattice-like grooves) to provide grooves 2.0mm in width, 0.5 mm in depth, and 15 mm in pitch. The pad was adhered toa disk of a polishing machine (“L/M-15E”, manufactured by Lapmaster SFTCorp.), by first providing Rodel Inc., Suba400 as the cushion layer andby then using double-sided adhesive tape (“442J”, manufactured by 3Mcom.) to adhere the pad thereon. Conditioning of the polishing pad wasperformed by using a conditioner (“CMP-M”, 14.2 cm in diameter,manufactured by Asahi Diamond Industrial Co., Ltd.), under a pressingpressure of 0.04 MPa for 5 minutes and supplying pure water at a rate of10 ml/min, while rotating the fixing disk at a rotation of 25 rpm androtating the conditioner at the same direction at a rotation of 25 rpm.The surface of the polishing pad was rinsed for 2 minutes while flowingpure water at a rate of 100 ml/min to the polishing machine, andsubsequently, a wafer having provided with an oxide film (a 4-inch dummywafer CZP type, manufactured by Shin-Etsu Chemical Co., Ltd.) was set tothe polishing machine, and polishing was performed thereon under apressing pressure of 0.04 MPa for 5 minutes, while rotating thepolishing platen at a rotation of 45 rpm and rotating the conditioner atthe same direction at a rotation of 45 rpm, and while supplying, at arate of 100 ml/min, a slurry dispersion (“SC-1”, manufactured by CabotMicroelectronics Corporation) having prepared at a concentrationdescribed in the instruction manual. Care was taken not to dry thesurface of the wafer by immediately supplying pure water, and the wafersurface was cleaned by using a polyvinyl alcohol sponge. Then, thesurface of the wafer was dried by blowing dry compressed air. The numberof dust particles 0.5 μm or larger in diameters, which were present onthe surface, was measured by using a wafer surface dust detectionapparatus (“WM-3” manufactured by TOPCON Co., Ltd.). In case dustparticles found are 400 counts or less may pass the present test, and noproblems are found in producing the semiconductor.

(Measurement of the Rate for Polishing Oxide Film)

The thickness of the oxide film on the surface of the wafer (a 4-inchdummy wafer CZP type, manufactured by Shin-Etsu Chemical Co., Ltd.) wasmeasured at 196 fixed points that were determined in advance by using“Lambda Ace” (VM-2000) manufactured by Dainippon Screen Mfg. Co., Ltd.The polishing pad to be tested was adhered to a platen of a polishingmachine (“L/M-15E”, manufactured by Lapmaster SFT Corp.), by firstproviding Rodel Inc., Suba400 as the cushion layer and by then usingdouble-sided adhesive tape (“442J”, manufactured by 3M com.) to adherethe pad thereon. Conditioning of the polishing pad was performed byusing a conditioner (“CMP-M”, 14.2 cm in diameter, manufactured by AsahiDiamond Industrial Co., Ltd.), under a pressing pressure of 0.04 MPa for5 minutes and supplying pure water at a rate of 10 ml/min, whilerotating the platen at a rotation of 25 rpm and rotating the conditionerat the same direction at a rotation of 25 rpm. The surface of thepolishing pad was rinsed for 2 minutes while flowing pure water at arate of 100 ml/min to the polishing machine, and subsequently, the waferhaving provided with an oxide film, whose thickness had been alreadymeasured, was set to the polishing machine, and polishing was performedthereon under a pressing pressure of 0.04 MPa for 5 minutes, whilerotating the platen at a rotation of 25 rpm and rotating the conditionerat the same direction at a rotation of 25 rpm, and while supplying, at arate of 100 ml/min, a slurry dispersion (“SC-1”, manufactured by CabotMicroelectronics Corporation) having prepared at a concentrationdescribed in the instruction manual. Care was taken not to dry thesurface of the wafer by immediately supplying pure water, and the wafersurface was cleaned by using a polyvinyl alcohol sponge. Then, thesurface of the wafer was dried by blowing dry compressed air. Thethickness of the oxide film provided on the surface of the wafer wasmeasured at 196 fixed points that were determined in advance by using“Lambda Ace” (VM-2000) manufactured by Dainippon Screen Mfg. Co., Ltd.).Thus, the polishing rate was calculated at each of the points, and theaverage value thereof was obtained as the polishing rate for the oxidefilm.

Then, conditioning of the polishing pad was performed only on the firstpolishing, and stability in polishing rate was evaluated by polishingthe wafer having thereon the oxide film after directly measuring thethickness of the oxide film without performing any conditioning of thepolishing pad from the second time.

(Evaluation of Dishing 1)

Test wafer for evaluating tungsten interconnection dishing: Grooves each100 μm in width and 0.7 μm in depth were formed at a space interval of100 μm on a 4-inch silicon wafer provided with an oxide film (2 μm inoxide film thickness). Tungsten coating was formed thereon by means ofsputtering at a thickness of 2 μm to obtain a test wafer for evaluatingtungsten interconnection dishing.

A circular polishing layer 38 cm in diameter was prepared, and thesurface thereof was subjected to a so-called X-Y groove processing(processing of lattice-like grooves) to provide grooves 2.0 mm in width,0.5 mm in depth, and 15 mm in pitch. The resulting polishing pad wasadhered to a platen of a polishing machine (“L/M-15E”, manufactured byLapmaster SFT Corp.), by first providing Rodel Inc., “Suba400” as thecushion layer and by then using a double-sided adhesive tape (“442J”,manufactured by 3M com.) to adhere the pad thereon. Conditioning of thepolishing pad was performed by using a conditioner (“CMP-M”, 14.2 cm indiameter, manufactured by Asahi Diamond Industrial Co., Ltd.), under apressing pressure of 0.04 MPa for 5 minutes and supplying pure water ata rate of 10 ml/min, while rotating the platen at a rotation of 25 rpmand rotating the conditioner at the same direction at a rotation of 25rpm. The surface of the polishing pad was rinsed for 2 minutes whileflowing pure water at a rate of 100 ml/min to the polishing machine, andsubsequently, the test wafer for evaluating tungsten interconnectiondishing was set to the polishing machine, and polishing was performedthereon under a pressing pressure of 0.04 MPa for 2 minutes, whilerotating the platen at a rotation of 45 rpm (at a linear velocity at thecenter of the wafer of 3000 (cm/min)) and rotating a semi-conductorwafer holding table at the same direction at a rotation of 45 rpm, andwhile supplying, at a rate of 100 ml/min, a 1:1 mixed slurry solution ofa slurry (“SEMI-SPERSE W-A400”, manufactured by Cabot MicroelectronicsCorporation) having prepared at a concentration described in theinstruction manual and an oxidizing agent (“SEMI-SPERSE FE-400”,manufactured by Cabot Microelectronics Corporation). Care was taken notto dry the surface of the wafer by immediately supplying pure water, andthe wafer surface was cleaned by using a polyvinyl alcohol sponge. Then,the surface of the wafer was dried by blowing dry compressed air. Thedishing state of the surface of the tungsten was measured by using adigital high definition microscope for ultra-depth profiling, “VK-8500”,manufactured by Keyence Corporation.

The morphology of the processed surface of the polishing layer wasmeasured according to the procedure taken for measuring othermorphologies. The center depth of the tungsten interconnection wasmeasured, and those yielding a measured value of 0.04 μm or less passedthe test.

(Evaluation of Dishing 2)

Explanation is made by making reference to FIGS. 1 and 2. FIG. 1 isdiagram showing schematically a 4-inch diameter wafer provided with anoxide film. The chip size is 10-mm square, and the chip pitch is 15 mm.Referring to FIG. 1, there is shown a center chip 1, and an edge chip 2.FIG. 2 is a diagram showing schematically an interconnection pattern ofan oxide film TEG, in which an interconnection pattern within a chiphaving a interconnection step difference of 0.45 μm. There are shown 25interconnection patterns (with 8 interconnection lines) each 2-mmsquare. Referring to the figure, shown are a pattern 3 with a protrudedportion/concave portion=230/20 (μm), a pattern 4 with a protrudedportion/concave portion=130/120 (μm), and a pattern 5 with a protrudedportion/concave portion=20/230 (>m).

The evaluation of dishing was performed by forming chips on a wafer (a4-inch dummy wafer CZP type, manufactured by Shin-Etsu Chemical Co.,Ltd.) at various line densities as shown in FIGS. 1 and 2, and thepolishing amount was measured on a 230-μm space portion (concave oxidefilm) by using “Lambda Ace” (VM-2000) manufactured by Dainippon ScreenMfg. Co., Ltd.

More specifically, the polishing pad to be tested was adhered to aplaten of a polishing machine (“L/M-15E”, manufactured by Lapmaster SFTCorp.), by first providing Rodel Inc., Suba400 as the cushion layer andby then using double-sided adhesive tape (“442J”, manufactured by 3Mcom.) to adhere the pad thereon. Conditioning of the polishing pad wasperformed by using a conditioner (“CMP-M”, 14.2 cm in diameter,manufactured by Asahi Diamond Industrial Co., Ltd.), under a pressingpressure of 0.04 MPa for 5 minutes and supplying pure water at a rate of10 ml/min, while rotating the fixing disk at a rotation of 25 rpm androtating the conditioner at the same direction at a rotation of 25 rpm.The surface of the polishing pad was rinsed for 2 minutes while flowingpure water at a rate of 100 ml/min to the polishing machine, andsubsequently, the wafer having provided with an oxide film and havingthe oxide film thickness measured on the 230-μm space portion and the20-μm line portion (protruded portion) provided as a pair, was set tothe polishing machine, and polishing was performed thereon under apressing pressure of 0.04 MPa for 1 minute, while rotating the platen ata rotation of 45 rpm and rotating the conditioner at the same directionat a rotation of 45 rpm, and while supplying, at a rate of 100 ml/min, aslurry dispersion (“SC-1”) manufactured by Cabot MicroelectronicsCorporation, having prepared at a concentration described in theinstruction manual. In this case, the evaluation of the fixed abrasivepad was made by using an aqueous KOH solution of pH 10.5 instead ofusing slurry dispersion. Care was taken not to dry the surface of thewafer by immediately supplying pure water, and the wafer surface wascleaned by using a polyvinyl alcohol sponge. Then, the surface of thewafer was dried by blowing dry compressed air. The thickness of theoxide film provided on the surface of the 230-μm space portion and the20-μm line portion provided as a pair was measured by using “Lambda Ace”(VM-2000) manufactured by Dainippon Screen Mfg. Co., Ltd.) to measurethe amount polished. Polishing was repeated carefully until the stepheight became 10 nm or less. The dishing characteristics is better forthe smaller amount of polishing (ideally, the value is 0) in the 230-μmspace portion in case the step height became 10 nm or less. The test canbe passed in case the amount of polishing falls in a range of 300 nm orless.

(Evaluation of Planarization Characteristics)

First, a test wafer for use in evaluating global step height wasprepared in the following procedure.

Test wafer for use in evaluating global step height: A 10-mm square diewas placed on a 4-inch silicon wafer provided with an oxide film (oxidefilm thickness: 2 μm). After performing mask exposure by using aphotoresist, a line 20 μm in width and 0.7 μm in height was providedtogether with a space of 230 μm by means of RIE to the left half of the10-mm square die in line-and-space arrangement, and a line 230 μm inwidth and 0.7 μm in height was provided together with a space of 20 μmto the right half in line-and-space arrangement.

A circular polishing layer 38 cm in diameter was prepared, and thesurface thereof was subjected to a so-called X-Y groove processing(processing of lattice-like grooves) to provide grooves 2.0 mm in width,0.5 mm in depth, and 15 mm in pitch. The resulting polishing pad wasadhered to a fixing disk of a polishing machine (“L/M-15E”, manufacturedby Lapmaster SFT Corp.), by first providing Rodel Inc., “Suba400” as thecushion layer and by then using a double-sided adhesive tape (“442J”,manufactured by 3M com.) to adhere the pad thereon. Conditioning of thepolishing pad was performed by using a conditioner (“CMP-M”, 14.2 cm indiameter, manufactured by Asahi Diamond Industrial Co., Ltd.), under apressing pressure of 0.04 MPa for 5 minutes and supplying pure water ata rate of 10 ml/min, while rotating the platen at a rotation of 25 rpmand rotating the conditioner at the same direction at a rotation of 25rpm. The surface of the polishing pad was rinsed for 2 minutes whileflowing pure water at a rate of 100 ml/min to the polishing machine, andsubsequently, the test wafer for use in evaluating global step heightwas set to the polishing machine, and polishing was performed thereonfor a predetermined time under a pressing pressure of 0.04 MPa, whilerotating the platen at a rotation of 45 rpm (at a linear velocity at thecenter of the wafer of 3000 (cm/min)) and rotating a semi-conductorwafer holding table at the same direction at a rotation of 45 rpm, andwhile supplying, at a rate of 100 ml/min, a slurry (“SC-1”) manufacturedby Cabot Microelectronics Corporation having prepared at a concentrationdescribed in the instruction manual. Care was taken not to dry thesurface of the wafer by immediately supplying pure water, and the wafersurface was cleaned by using a polyvinyl alcohol sponge. Then, thesurface of the wafer was dried by blowing dry compressed air. Thethickness of the oxide film of the 20-μm line and the 230-μm line in thecenter 10-mm die of the test wafer for evaluating global step height wasmeasured for each by using “Lambda Ace” (VM-2000) manufactured byDainippon Screen Mfg. Co., Ltd.), and the difference in thickness wasevaluated as the global step height. The morphology of the processedsurface of the polishing layer was measured according to the proceduretaken for measuring other morphologies. Those yielding a global stepdifference of 45 nm or less between the 20-μm line region and the 230-μmline region in a polishing time of 5 minutes passed the test.

(Measurement of D Hardness)

Samples falling in a thickness range of from 1.0 mm to 1.5 mm (andhaving a size of 1-cm square or larger) were placed on a plane havingsuch a surface hardness of D hardness value of 90 or higher, and Dhardness was measured on 5 points by using a Durometer Type D (inpractice, using “Askar D-type hardness meter” manufactured by KobunshiKeiki Co., Ltd.) in accordance with JIS standard (hardness test) K6253.The measurement was carried out at room temperature (25° C.).

(Measurement of Flexural Modulus of Elasticity)

A rectangular test piece 1×8.5 cm in size and ranging from 1.0 mm to 1.5mm in thickness was prepared from the polishing pad. Measurement offlexural modulus of elasticity was performed on the test piece inaccordance with JIS-7203 by using a material testing machine (TensilonRTM-100) manufactured by ORIENTEC Co., Ltd. The flexural modulus ofelasticity was obtained in accordance with the equation as follows(wherein, the distances are given in units of millimeter):Flexural modulus of elasticity={(Distance between supportingpoints)³×(load (kgf) at a point arbitrarily selected from the linearportion in the initial part of the load−deflection curve)}/{4×(width ofthe test piece)×(thickness of the test piece)³×(deflection on applying aload of F)}.(Measurement of Water Absorptivity and Rate of Water Absorption)

The test piece (25×60 mm in size, any thickness) cut out from thepolishing pad was subjected to vacuum drying at 80° C. for 10 hours, andwas then immersed in pure water at room temperature. Test pieces wereeach taken out from pure water after 5 minutes, 30 minutes, 60 minutes,3 hours, and 10 hours, and were each placed inside a centrifugal tube.Thus, centrifugal force ranging from 1400 G to 1450 G was applied to thetube for 30 minutes to drive out water. The hygroscopic weight was thenmeasured on the resulting products.

Water absorptivity was obtained in accordance with the followingequation:Water absorptivity (%)={(hygroscopic weight at time 1)−(dryweight)}/(dry weight)×100.Then, the rate of water absorption was obtained in accordance with thefollowing equation, where time 1 and time 2 are taken in the unit ofminutes:Rate of water absorption (%/hr)=(Water absorptivity at time 2)−(Waterabsorptivity at time 1))×60/(time 2 −time 1).

More specifically, for instance, in case time 1 is 5 minutes and time 2is 30 minutes, the average rate of water absorption can be obtained fora time interval of 5 minutes to 30 minutes from the initiation ofmoisture absorption. In the present patent, the average rate of moistureabsorption up to 5 minutes was obtained.

(Measurement of Centerline Average Roughness Ra)

A circular polishing pad 38 cm in diameter and 1.2 mm in thickness wasprepared, and a desired lattice-like groove patterning or dimplepatterning was provided to the surface thereof. The resulting polishingpad was adhered to a platen of a polishing machine (“L/M-15E”,manufactured by Lapmaster SFT Corp.), by first providing Rodel Inc.,“Suba400” as the cushion layer and by then using a double-sided adhesivetape (“442J”, manufactured by 3M com.) to adhere the pad thereon.Conditioning of the polishing pad was performed by using a conditioner(“CMP-M”, 14.2 cm in diameter, manufactured by Asahi Diamond IndustrialCo., Ltd.), under a pressing pressure of 0.04 MPa for 5 minutes andsupplying pure water at a rate of 10 ml/min, while rotating the platenat a rotation of 25 rpm and rotating the conditioner at the samedirection at a rotation of 25 rpm. The surface of the polishing pad wasthen rinsed for 2 minutes while flowing pure water at a rate of 100ml/min to the polishing machine. Subsequently, by using a surfaceroughness meter (“Surfocorder SE-3300”) produced by Kosaka LaboratoryInc., measurement was made for 8-mm length each at 5 points startingfrom a position 7 cm distant from the center of the polishing pad alongthe radius direction, and then increasing the distance every time by 1cm. In case the measuring point fell on the groove, the measuring pointwas displaced for a minimal length. The measuring conditions followedthose recommended by JIS (i.e., the cut off value was 0.8 mm, and themeasuring speed was 0.1 mm/second). The average value of the observedvalues for 5 points was used as the Ra value. Then, the pad was adheredagain to a platen of a polishing machine (“L/M-15E”, manufactured byLapmaster SFT Corp.), by first providing Rodel Inc., “Suba400” as thecushion layer and by then using a double-sided adhesive tape (“442J”,manufactured by 3M com.) to adhere the pad thereon. A wafer having anoxide film provided thereon (a 4-inch dummy wafer CZP type, manufacturedby Shin-Etsu Chemical Co., Ltd.) was set to the polishing machine, andpolishing was performed thereon under a pressing pressure of 0.04 MPafor 5 minutes, while rotating the platen at a rotation of 45 rpm androtating the conditioner at the same direction at a rotation of 45 rpm,and while supplying, at a rate of 100 ml/min, a slurry dispersion(“SC-1”, manufactured by Cabot Microelectronics Corporation) havingprepared at a concentration described in the instruction manual. Thesurface of the polishing pad was then rinsed for 2 minutes while flowingpure water at a rate of 100 ml/min to the polishing machine, and thecenterline roughness Ra was measured in accordance with the procedureabove (if necessary, this procedure is repeated for times correspondingto the number of wafer sheets).

(On the Effect of Water Supply Mechanism)

Example 1

Two sheets of filter paper 17 chr produced by Whatman Corporation weresuperposed, and were impregnated with a mixed solution containing 20parts of polyvinyl pyrrolidone (having a molecular weight of 10000) and80 parts of a 999/1 mixture of MMA (methyl methacrylate)/AIBN(azobis(isobutyronitrile)). The resulting product was interposed betweenglass sheets, and polymerization was carried out by placing them insidea hot bath of 65° C. for 5 hours. The polymerization was completed byallowing it to stand for 3 hours in a dryer held at 100° C. Dustadhesion test was carried out on the thus obtained resin sheet. As aresult, 151 dust particles were observed, and the D hardness was foundto be 83 degrees. The polishing rate of the oxide film was found to be132 nm/min. The filter paper portion functioned as a water supplyingmechanism, and the dust adhesion to the surface of the article to bepolished was reduced. Further, the domain size was found to be 3.6×10⁻⁵m² under the microscope.

Example 2

A filter paper powder (E type) produced by ADVANTEK Co. Ltd. wasuniaxially kneaded and compounded with “Surlyn” (1705, product of MitsuiDuPont Polychemicals, K.K.) at 165° C. in such a manner that the powderpaper should account for 35% by weight. Pellets cut into 3 mm in lengthwere hot pressed at 185° C. in a 40-cm square mold. The resin sheet thusobtained was subjected to a dust adhesion test.

As a result, 254 dust particles were observed, and the D hardness wasfound to be 63 degrees.

The polishing rate of the oxide film was found to be 32 nm/min. Thepowder of the filter paper functioned as a water supplying mechanism,and the dust adhesion to the surface of the article to be polished wasreduced. Further, the domain size was found to be 4.3×10⁻¹⁰ m² under themicroscope.

Comparative Example 1

A 40-cm square “Axtar” (a product of Toray Industries, Inc.; a non-wovenmade of polyethylene terephthalate filaments, density 280 g/m²) wasimpregnated with liquid phenolic resin (PR-53123, a product of SumitomoDurez K.K.) at a dry weight ratio of 50 wt %, dried, and shaped at 170°C. for 20 minutes under pressure of 3.5 MPa to obtain a sheet 1.2 mm inthickness. As a result, 3234 dust particles were observed. The Dhardness was found to be 90 degrees. The polishing rate of the oxidefilm was found to be 111 nm/min. The polyethylene terephthalatefilaments were found impossible to function as a water supply mechanism,and the dust adhesion to the surface of the article to be polished couldnot be reduced.

Comparative Example 2

Hot press molding was performed by using a 40-cm square mold at 185° C.in a manner similar to that described in Example 2, except for usingpellets of “Surlyn” in the place of filter paper powder. The dustadhesion test was performed on the thus obtained resin sheet. As aresult, 3443 dust particles were observed. The D hardness was found tobe 64 degrees. The polishing rate of the oxide film was found to be 35nm/min. Because filter paper powder was used, it was found unable toestablish a water supply mechanism domain, and the dust adhesion to thesurface of the article to be polished could not be reduced.

(On the Effect of the Hydrophilic Polymers Substantially Insoluble toWater)

Example 3

A sheet of filter paper 17 chr produced by Whatman Corporation wasimpregnated with 999/1 mixed MMA (methyl methacrylate)/AIBN(azobis(isobutyronitrile)). The resulting product was interposed betweenglass sheets, and polymerization was carried out by placing them insidea hot bath of 65° C. for 5 hours. Then, the product was allowed to standin a dryer at 100° C. for 3 hours to complete the polymerization. Dustadhesion test was performed on the resulting resin sheet. As a result,201 dust particles were observed. The D hardness was found to be 88degrees. The solubility parameter of the filter paper, i.e., cellulose,was found to yield δsp of 24.08 and δh of 11.85.

Example 4

A filter paper powder (E type) produced by ADVANTEK Co. Ltd. wasuniaxially kneaded and compounded with “Surlyn” (1705, product of MitsuiDuPont Polychemicals, K.K.) at 165° C. in such a manner that the powderpaper should account for 30% by weight. Pellets cut into 3 mm in lengthwere hot pressed at 185° C. in a 40-cm square mold. The resin sheet thusobtained was subjected to a dust adhesion test.

As a result, 327 dust particles were observed, and the D hardness wasfound to be 63 degrees.

The polishing rate of the oxide film was found to be 35 nm/min. Thesolubility parameter of the filter paper, i.e., cellulose, was found toyield δsp of 24.08 and δh of 11.85.

Example 5

A 40-cm square “Kevlar” felt (product of Toray DuPont K.K., density 280g/m²) was impregnated with liquid phenolic resin (PR-53123, a product ofSumitomo Durez K.K.) at a dry weight ratio of 50 wt %, dried, and shapedat 170° C. for 20 minutes under pressure of 3.5 MPa to obtain a sheet1.2 mm in thickness. As a result, 196 dust particles were observed. TheD hardness was found to be 90 degrees. The polishing rate of the oxidefilm was found to be 88 nm/min. The solubility parameter of “Kevlar”,i.e., an aromatic polyamide, was found to yield δsp of 15.89 and δh of9.27.

Comparative Example 3

Similar to Example 1, a 999/1 mixture of MMA (methyl methacrylate)/AIBN(azobis(isobutyronitrile)) was polymerized between sheets without usinga filter paper, and dust adhesion test was carried out by using the thusobtained resin sheet. As a result, 2291 dust particles were observed.The D hardness was found to be 91 degrees. The polishing rate of theoxide film was found to be 350 nm/min.

Comparative Example 4

Similar to Example 2, pellets of “Surlyn” were used without using filterpaper powder, and were hot pressed at 185° C. in a 40-cm square mold.The resin sheet thus obtained was subjected to a dust adhesion test. Asa result, 3443 dust particles were observed, and the D hardness wasfound to be 64 degrees. The polishing rate of the oxide film was foundto be 35 nm/min.

(Particles and/or Fibrous Material Made of Hydrophilic Organic MaterialHaving a Water Absorptivity of 5000% or Lower)

The evaluation results (flexular modulus of elasticity, D hardness, dustadhesion, polishing rate of oxide film, evaluation of planarizationcharacteristics, and the measurement of dishing) obtained on Examplesand Comparative Examples are shown in Table 1. The interstices wereconfirmed by using an optical microscope at a magnification of 50 times.

Example 6

A mixture comprising 35 parts by weight of polyvinyl polypyrrolidone(having nominal water content of 6% and water absorptivity of 2500%) and65 parts by weight of a 999/1 mixture of MMA (methyl methacrylate)/AIBN(azobis(isobutyronitrile)) was polymerized between sheets, and apolishing pad 1.2 mm in thickness was produced from the resin sheet thusobtained. No interstices were found in polyvinyl polypyrrolidone.

Example 7

A mixture comprising 33 parts by weight of polyvinyl polypyrrolidone(having nominal water content of 6% and water absorptivity of 2500%), 64parts by weight of a 999/1 mixture of MMA (methyl methacrylate)/AIBN(azobis(isobutyronitrile)), and 3 parts by weight of silica particles 1μm in particle diameter was polymerized between sheets, and a polishingpad was produced from the resin sheet thus obtained. No interstices werefound in polyvinyl polypyrrolidone.

Example 8

A 35 parts by weight portion of a filter paper powder (E type, havingnominal water content of 10% and water absorptivity of 500%) produced byADVANTEK Co. Ltd. was mixed with 65 parts by weight of a materialcontaining mixed therein “Artfirmer” (TA-1327, produced by SanyoChemical Industries, Inc.) at a predetermined mixing ratio, and theresulting mixture was fed inside a 40-cm square mold. After defoaming at100° C., the product was heated at 165° C. to obtain a resin sheet. Apolishing pad 1.2 mm in thickness was produced from the thus obtainedresin sheet. On observing the cross section with an optical microscope,no interstices were found in the filter paper powder.

Example 9

Sixty-two parts by weight of a two-part polyurethane resin C-4403 (aproduct of Nippon Polyurethane K.K.) was kneaded together with 38 partsby weight of N-4276 (a product of Nippon Polyurethane K.K.), and afterkneading the resulting product with 33 parts by weight of polyvinylpolypyrrolidone (having nominal water content of 6% and waterabsorptivity of 2500%), the product was hardened in a mold aftersubjecting it to vacuum degassing. Thus was obtained a 1.2 mm thickpolyurethane sheet. A polishing pad was produced from the resin sheetthus obtained. On observing the cross section with an opticalmicroscope, no interstices were found in polyvinyl polypyrrolidone.

Example 10

Seventeen parts by weight of powdered filter paper (KC-FLOCK produced byNippon Papermaking Industry Co., Ltd., 400-mesh size, having nominalwater content of 11% and water absorptivity of 500%) was kneaded with aliquid phenolic resin (PR-53717, a product of Sumitomo Durez K.K.) toyield a dry weight ratio of 83 parts by weight, and after drying, theproduct was shaped under pressure of 3.5 MPa at 170° C. for 20 minutesto obtain a sheet 1.2 mm in thickness. A polishing pad was produced fromthe resin sheet thus obtained. On observing the cross section with anoptical microscope, no interstices were found in the powdered filterpaper.

Example 11

A 1.2 mm thick polishing pad was produced in the same manner as inExample 10, except for mixing, in addition to the powdered filter paper,3 parts by weight of silica particles having a diameter of 1 μm, and forkneading the resulting mixture with a liquid phenolic resin (PR-53717, aproduct of Sumitomo Durez K.K.) to yield a dry weight of 80 parts byweight. On observing the cross section with an optical microscope, nointerstices were found in the powdered filter paper.

Example 12

Forty parts by weight of Nylon 6 particles having a diameter of 5 μm(and having nominal water content of 4.5% and water absorptivity of 22%)was kneaded with a liquid phenolic resin (PR-55123, a product ofSumitomo Durez K.K.) to yield a dry weight ratio of 60 parts by weight,and after drying, the product was shaped under pressure of 4 MPa at 170°C. for 20 minutes to obtain a sheet 1.2 mm in thickness. A polishing padwas produced from the resin sheet thus obtained. On observing the crosssection with an optical microscope, no interstices were found in theNylon particles.

Example 13

Forty-five parts by weight of polyacrylonitrile fibers having a diameterof 13 μm and cut into length of 100 μm (a product of Toray Industries,Inc., having nominal water content of 2% and water absorptivity of 15%)were kneaded together with 55 parts by weight of phenolic resin(BRP-5980, a product of Showa Highpolymer Co., Ltd.). The resultingproduct was fed inside a 40-cm square mold, and was shaped underpressure of 3.5 MPa at 185° C. for 20 minutes to obtain a sheet 1.2 mmin thickness. A polishing pad was produced from the resin sheet thusobtained. On observing the cross section with an optical microscope, nointerstices were found in the polyacrylonitrile fibers.

Example 14

A polyurethane block (normal water content: 1%, water absorptivity:3.5%) was ground to have a size such that it passed through a 300-meshfiler. Forty-five parts by weight of this polyurethane block was kneadwith 55 parts by weight of a phenolic resin (BRP-5980), a product ofShowa Highpolymer Co., Ltd.). The mixture was poured into a 40-cm squaremold and shaped under a pressure of 3.5 MPa at 185° C. for 20 minutes toobtain a sheet having a thickness of 1.2 mm. A polished pad was producedfrom the resin sheet thus obtained. On observing the cross section withan optical microscope, no interstices were found in the polyurethaneparticles.

Examples 15 to 20

The same procedures as described in Examples 8 to 13 were followed toobtain 1.2 mm thick polishing resin sheets each, except for adding 0.2parts by weight each of xanthane rubber as a hydrophilic water-solubleresin.

Example 21

The same procedure as described in Example 10 was followed, except forcontrolling pressure reduction during shaping the resin sheet to forminterstices in the powdered filter paper and the phenolic resin. Apolishing pad was produced from the thus obtained resin sheet.

Example 22

The same procedure as described in Example 21 was followed to obtain ashaped resin sheet, except for mixing, in addition to the powderedfilter paper, 30 parts by weight of silica particles having a diameterof 1 μm. A polishing pad was produced from the thus obtained resinsheet.

Example 23

A polishing resin sheet was fabricated by following the same procedureas that described in Example 10, except for further adding 7 parts byweight of xanthane rubber as a hydrophilic water-soluble resin. Onobserving the cross section with an optical microscope, interstices werefound in the powdered filter paper.

Comparative Example 5

Sanfresh ST10OMPS (manufactured by Sanyo Chemical Industries, Ltd.,having water absorptivity of 10000%) was impregnated with liquidphenolic resin (PR-55123, a product of Sumitomo Durez K.K.) to yield adry weight ratio of 50 parts by weight, and, after drying, the productwas shaped under pressure of 3.5 MPa at 170° C. for 20 minutes to obtaina sheet 1.2 mm in thickness. A polishing pad was produced from the resinsheet thus obtained. Large amount of swelled Sanfresh was observed toadhere on the wafer during polishing, and clean surface could not bemaintained. On observing the cross-section with an optical microscope,no interstices were found in Sanfresh.

Comparative Example 6

Hydrophobic polyethylene terephthalate fibers (having nominal watercontent of 0.4%, a diameter of 13 μm, and a length of 100 μm) wereimpregnated with liquid phenolic resin (PR-55123, a product of SumitomoDurez K.K.) to yield a dry weight ratio of 50 parts by weight, and,after drying, the product was shaped under pressure of 3.5 MPa at 170°C. for 20 minutes to obtain a sheet 1.2 mm in thickness. It was foundunfeasible to reduce dust adhesion to the surface of the article beingpolished. On observing the cross section with an optical microscope, nointerstices were found in the polyethylene terephthalate fibers.

Comparative Example 7

A 3.5-parts by weight portion of urethane particles described in Example9 was mixed with 96.5 parts by weight of a 999/1 mixture of MMA (methylmethacrylate)/AIBN (azobis(isobutyronitrile)), and the resulting productwas allowed to polymerize between plates. A 1.2 mm thick polishing padwas produced from the resin sheet thus obtained. Interstices wereobserved in the urethane particles.

Comparative Example 8

The same procedure as described in Examples 6 was followed, except formixing 3.5-parts by weight of polyvinyl polypyrrolidone with 96.5 partsby weight of a 999/1 mixture of MMA (methyl methacrylate)/AIBN(azobis(isobutyronitrile)), and for allowing the resulting product topolymerize between plates. A 1.2 mm thick polishing pad was producedfrom the resin sheet thus obtained. No interstices were observed inpolyvinyl polypyrrolidone.

TABLE 1 Evaluation of Planrization Flexural Modulus Polishing rate of(Polishing Measurement of of Elasticity D hardness Dust adhesion Scratchflaws Oxide film time/step height) Dishing (GPa) (degrees) (particles)(counts) (nm/min) (min/nm) (um) Examples  6 4 89 301 0 199 5/34 0.03  79 91 321 2 208 4/32 0.02  8 3 85 258 1 112 5/42 0.04  9 2 77 289 2 1085/32 0.04 10 6 89 299 4 87 5/22 0.03 11 12 92 335 5 107 4/29 0.02 12 589 248 2 99 4/34 0.03 13 5 89 315 1 116 4/35 0.03 14 5 89 356 2 118 4/360.03 15 3 89 301 0 205 5/36 0.03 16 9 91 321 2 216 4/34 0.02 17 3 85 2581 127 5/42 0.04 18 2 77 289 2 115 5/35 0.04 19 6 89 299 4 92 5/28 0.0320 11 92 335 5 114 5/22 0.02 21 6 89 301 4 107 5/29 0.03 22 13 93 355 4132 4/28 0.02 23 5 87 265 2 83 5/22 0.03 Comp  5 4 88 426 2 79 5/88 0.05Ex  6 4 88 3,426 13 84 5/88 0.05  7 4 89 4,331 321 259 5/31 0.03  8 4 893,884 284 279 5/34 0.03(Effect of Mixing Sheet-like Materials)

The evaluation results (flexural modulus of elasticity, D hardness, dustadhesion, polishing rate of oxide film, evaluation of planarizationcharacteristics, and measurement of dishing 1) obtained on Examples andComparative Examples are given in Table 2. The interstices wereconfirmed by using optical microscope at a magnification of 50 times.

Example 24

Two sheets of filter paper 17chr (having nominal water content of 11%and a dry thickness of 0.9 mm) produced by Whatman Corporation weresuperposed, and the resulting product was impregnated with 65 parts of a999/1 mixture of MMA (methyl methacrylate)/AIBN(azobis(isobutyronitrile)). The resulting product was interposed betweenglass sheets, and polymerization was carried out by placing them insidea hot bath of 65° C. for 5 hours. The polymerization was completed byallowing it to stand for 3 hours in a dryer held at 100° C. A polishingpad was produced from the thus obtained resin sheet. On observing thecross section with an optical microscope, no interstices were observedin the filter paper.

Example 25

Two sheets of filter paper 17 chr (having nominal water content of 11%and a dry thickness of 0.9 mm) produced by Whatman Corporation weresuperposed, and the resulting product was impregnated with liquidphenolic resin (PR-55123, a product of Sumitomo Durez K.K.) to yield adry weight ratio of 50 parts by weight. After drying, the resultingproduct was shaped under pressure of 3.5 MPa at 170° C. for 20 minutesto obtain a sheet 1.8 mm in thickness. A 1.2 mm thick polishing pad wasproduced from the thus obtained resin sheet. On observing the crosssection with an optical microscope, no interstices were observed in thefilter paper.

Example 26

A craft paper (having nominal water content of 10%) 0.18 mm in thicknesswas impregnated with a liquid phenolic resin (PR-55123, a product ofSumitomo Durez K.K.) to yield a dry weight ratio of 50 parts by weight.After drying, six sheets of the paper were superposed, and the resultingproduct was shaped under pressure of 3.5 MPa at 170° C. for 20 minutesto obtain a sheet 1.2 mm in thickness. A polishing pad was produced fromthe thus obtained resin sheet. On observing the cross section with anoptical microscope, no interstices were observed in the craft paper.

Example 27

Fifty-one parts by weight of two-part polyurethane resin C-4421(manufactured by Nippon Polyurethane Industry Co., Ltd.) was kneadedwith 49 parts by weight of N-4276 (manufactured by Nippon PolyurethaneIndustry Co., Ltd.), and a cellulose sponge (a product of Toray FineChemicals, Inc., having nominal water content of 11% and adry-compressed thickness of 1 mm) was impregnated with the resultingproduct to yield a weight ratio of 25 parts by weight. After defoamingin vacuum, the resulting product was hardened in a mold to produce apolyurethane sheet 1.2 mm in thickness. A polishing pad was producedfrom the resin sheet thus obtained. On observing the cross section withan optical microscope, no interstices were observed in the cellulosesponge.

Example 28

Thirty parts by weight of a Nylon woven material (300 μm in thicknessand having nominal water content of 4.5%) was impregnated with liquidphenolic resin (PR-53717, a product of Sumitomo Durez K.K.) to yield adry weight ratio of 70 parts by weight. After drying, 4 sheets of theresulting product were superposed and shaped under pressure of 3.5 MPaat 170° C. for 20 minutes to obtain a sheet 1.2 mm in thickness. Apolishing pad was produced from the thus obtained resin sheet. Onobserving the cross section with an optical microscope, interstices wereobserved in the Nylon woven material.

Example 29

Thirty parts by weight of a cotton woven material (300 μm in thicknessand having nominal water content of 10%) was impregnated with liquidphenolic resin (PR-53717, a product of Sumitomo Durez K.K.) to yield adry weight ratio of 70 parts by weight. After drying, 4 sheets of theresulting product were superposed and shaped under pressure of 3.5 MPaat 170° C. for 20 minutes to obtain a sheet 1.2 mm in thickness. Apolishing pad was produced from the thus obtained resin sheet. Onobserving the cross section with an optical microscope, no intersticeswere observed in the cotton woven material.

Example 30

Sixty-five parts by weight of a material containing mixed therein“Artfirmer” (TA-1327, produced by Sanyo Chemical Industries, Inc.) at apredetermined mixing ratio was mixed with a craft paper 0.24 mm inthickness (having nominal water content of 10%), and 5 sheets of theresulting product were superposed and placed inside a 40-cm square mold.After defoaming at 100° C., the resulting product was heated at 165° C.to obtain a resin sheet. A polishing pad was produced with the resinsheet thus obtained. On observing the cross section with an opticalmicroscope, no interstices were observed in the craft paper.

Example 31

Three sheets each of the prepregs produced in Examples 26 and 30 beforeshaping were superposed alternately with “Artfirmer” in such a mannerthat “Artfirmer” may become on the upper side, and after shaping a resinsheet similarly, a polishing pad was produced therefrom. No intersticeswere found in the craft paper.

Example 32

Three sheets each of the prepregs produced in Examples 26 and 28 beforeshaping were superposed alternately in such a manner that the craftpaper may be disposed on the upper side, and after shaping a resin sheetsimilarly, a polishing pad was produced therefrom. No interstices werefound in the craft paper and the Nylon woven material.

Example 33

Similar procedure as that described in Example 32 was followed, exceptfor placing a 4 μm thick polyethylene terephthalate film under theprepregs produced in Examples 26 and 28. Three sets of such arrangementwere alternately stuck to shape a 9-layred resin sheet. No intersticeswere found in the craft paper and the Nylon woven material.

Example 34

The same procedure as that described in Example 26 was followed toproduce a polishing pad, except for using, as a matrix resin, a liquidphenolic resin (PR-55123, a product of Sumitomo Durez K. K.) containingmixed therein 3 parts by weight of silica particles having a diameter of1 μm. On observing the cross section with an optical microscope, nointerstices were observed in the craft paper.

Example 35

The same procedure as that described in Example 34 was followed toproduce a polishing pad, except for using a liquid phenolic resin(PR-55123, a product of Sumitomo Durez K.K.) containing mixed therein 30parts by weight of silica particles. On observing the cross section withan optical microscope, no interstices were observed in the craft paper.

Examples 36 to 38

The same procedures as described in Examples 33 to 35 were followed toobtain polishing resin sheets each, except for adding 0.4 parts byweight each of xanthane rubber as a hydrophilic water-soluble resin. Nointerstices were observed in each of the resulting products.

Example 39

The same procedure as described in Example 33 was followed, except forcontrolling pressure reduction during shaping the resin sheet to forminterstices in the craft paper. A polishing pad was produced from thethus obtained resin sheet.

Example 40

The same procedure as described in Example 33 was followed, except forcontrolling pressure reduction during shaping the resin sheet to forminterstices in both of the craft paper and the phenolic resin. Apolishing pad was produced from the thus obtained resin sheet.

Example 41

A woven material of polyacrylonitrile fibers (produced by TorayIndustries, Inc., 300 μm thick and having nominal water content of 2%)was impregnated with a liquid phenolic resin (PR-53717, a product ofSumitomo Durez K.K.) in such a manner to yield a dry weight of 55 partsby weight. After drying, 4 sheets of the resulting product weresuperposed, and were shaped under pressure of 3.5 MPa at 170° C. for 20minutes to obtain a sheet 1.2 mm in thickness. A polishing pad wasproduced from the thus obtained resin sheet. On observing the crosssection with an optical microscope, no interstices were observed in thewoven material of polyacrylonitrile fibers.

Example 42

A woven material of thermoplastic urethane fibers (300 μm thick, 13 μmin fiber diameter, and having nominal water content of 1%) wasimpregnated with a liquid phenolic resin (PR-53717, a product ofSumitomo Durez K.K.) in such a manner to yield a dry weight of 55 wt %.After drying, 4 sheets of the resulting product were superposed, andwere shaped under pressure of 3.5 MPa at 170° C. for 20 minutes toobtain a sheet 1.2 mm in thickness. A polishing pad was produced fromthe thus obtained resin sheet. On observing the cross section with anoptical microscope, interstices were observed in the woven material ofpolyurethane fibers.

Example 43

A polishing resin sheet was fabricated by following the same procedureas that described in Example 33, except for further adding 5 parts byweight of xanthane rubber as a hydrophilic water-soluble resin. Nointerstices were found.

Example 44

Thirty parts by weight of a 0.24 mm thick craft paper (having nominalwater content of 10%) was impregnated with molten polypropylene, and theinterstices thereof were coated with liquid phenolic resin (PR-53717, aproduct of Sumitomo Durez K.K.) at a thickness of 2 μm. Five sheets ofthe resulting product were placed together inside a 40-cm square mold,and were subjected to pressing at 190° C. A polishing pad was producedfrom the thus obtained resin sheet. On observing the cross section withan optical microscope, no interstices were observed in the craft paper.

Example 45

A 0.24 mm thick craft paper (having nominal water content of 10%) wasimpregnated with a melt kneaded 95/5 (weight ratio) mixture ofpolypropylene and silica particles having pores 1 μm in pore diameter insuch a manner that in total they become 30 parts by weight. Five sheetsof the resulting product were placed together inside a 40-cm squaremold, and were subjected to pressing at 190° C. A polishing pad wasproduced from the thus obtained resin sheet. On observing the crosssection with an optical microscope, no interstices were observed in thecraft paper.

Comparative Example 9

Anon-woven cloth of polyethylene terephthalate filaments (a product ofToray Industries, Inc., having a density of 100 g/m² and nominal watercontent of 0.4%, with filament diameter of 13 μm) was impregnated withliquid phenolic resin (PR-55123, a product of Sumitomo Durez K.K.) insuch a manner that the weight ratio may become 4 parts by weight. Afterdrying, 5 sheets of the resulting product were shaped under pressure of3.5 MPa at 170° C. for 20 minutes to obtain a sheet 1.4 mm in thickness.A polishing pad was produced from the thus obtained resin sheet. Onobserving the cross section with an optical microscope, no intersticeswere observed in the non-woven cloth of polyethylene terephthalatefilaments.

Comparative Example 10

Five sheets of non-woven cloth of polyethylene terephthalate filaments(a product of Toray Industries, Inc., having a density of 100 g/m² andnominal water content of 0.4%, with filament diameter of 13 μm) weresuperposed, and after mixing therein 60 parts by weight of a 999/1mixture of MMA (methyl methacrylate)/AIBN (azobis(isobutyronitrile)),polymerization between sheets was performed at a weight ratio of 40%. Apolishing pad was produced from the thus obtained resin sheet. Onobserving the cross section with an optical microscope, no intersticeswere observed in the non-woven cloth of polyethylene terephthalatefilaments.

TABLE 2 Evaluation of Planrization Flexural Modulus Polishing rate of(Polishing Measurement of of Elasticity D hardness Dust adhesion Scratchflaws Oxide film time/step height) Dishing (GPa) (degrees) (particles)(counts) (nm/min) (min/nm) (um) Examples 24 4.6 90 289 3 183 5/30 0.0325 9.3 91 261 2 83 5/38 0.04 26 8.6 90 244 1 82 5/38 0.04 27 3.5 77 2892 102 5/33 0.04 28 5.8 89 364 8 108 5/31 0.03 29 5.7 90 268 2 87 5/350.04 30 6.2 86 258 1 78 4/42 0.03 31 6.0 90 244 0 88 5/33 0.03 32 5.1 89356 2 96 4/36 0.03 33 6.5 89 287 0 101 5/31 0.03 34 9.5 90 258 2 1124/40 0.03 35 15.3 93 288 6 142 4/32 0.03 36 8.3 89 241 1 84 5/31 0.04 379.2 90 255 2 110 4/28 0.03 38 14.5 93 281 5 132 4/22 0.02 39 5.8 87 2352 85 5/38 0.04 40 5.8 86 223 1 93 5/38 0.04 41 5.5 89 315 1 116 5/350.03 42 5.8 89 356 2 118 5/36 0.03 43 7.6 87 228 1 80 5/31 0.03 44 3.475 287 1 70 5/38 0.04 45 3.5 76 305 2 73 5/37 0.04 Comp  9 4.4 88 3,42638 84 5/88 0.05 Ex. 10 3.5 89 4,331 321 259 5/31 0.03(On the Mixing Effect of Fibrous Materials Having an Aspect Ratio of 5or Higher and/or Particles Formed from the Composites Thereof)

The evaluation results (flexular modulus of elasticity, D hardness, dustadhesion, polishing rate of oxide film, evaluation of planarizationcharacteristics, and the measurement of dishing) obtained on Examplesand Comparative Examples are shown in Table 3. The interstices wereconfirmed by using an optical microscope at a magnification of 50 times.

Example 46

Thirty-five parts by weight of ultrafine fibers having a core and sheathstructure (30 μm in diameter, comprising polystyrene for the matrix, andhaving nominal water content of 5%) using polyvinyl alcohol as the coreand cut to a length of 3 mm (having an aspect ratio of 100) was mixedwith 65 parts by weight of a 999/1 mixture of MMA (methylmethacrylate)/AIBN (azobis(isobutyronitrile)), and polymerizationbetween sheets was performed thereon. A polishing pad, was produced fromthe resulting resin sheet. On observing the cross section with anoptical microscope, no interstices were observed in the fibers made ofpolyvinyl alcohol.

Example 47

A powdered filter paper (having nominal water content of 11%)manufactured by Tosco Co., Ltd. was uniaxially kneaded at 160° C. withpolypropylene (manufactured by Mitsubishi Chemicals Co., Ltd.) to obtaina compound in such a manner that the former may account for 18 wt %. Thepowdered filter paper manufactured by Tosco Co., Ltd. is such obtainedby cutting linen at a length of about 25 μm, and exhibits fibrilstructure about 1 μm in thickness (with aspect ratio of about 25). Byusing pellets cut to a length of 3 mm, hot press molding was performedat 185° C. by using a 40-cm square mold. A polishing pad was producedfrom the resin sheet thus obtained. On observing the cross section withan optical microscope, no interstices were observed in the powderedfilter paper.

Example 48

A powdered filter paper (having nominal water content of 11% and anaspect ratio of about 25) manufactured by Tosco Co. Ltd. was impregnatedwith liquid phenolic resin (PR-55123, a product of Sumitomo Durez K.K.)in such a manner that the dry weight ratio may become 55 parts byweight. After drying, the resulting product was shaped under pressure of3.5 MPa at 170° C. for 20 minutes to obtain a sheet 1.2 mm in thickness.A polishing pad was produced from the thus obtained resin sheet. Onobserving the cross section with an optical microscope, no intersticeswere observed in the powdered filter paper.

Example 49

A powdered filter paper (having nominal water content of 11% and anaspect ratio of about 25) manufactured by Tosco Co., Ltd. was mixed with45 parts by weight of a material containing mixed therein “Artfirmer”(TA-1327, produced by Sanyo Chemical Industries, Inc.) at apredetermined mixing ratio, and the resulting mixture was fed inside a40-cm square mold. After defoaming at 100° C., the product was heated at165° C. to obtain a resin sheet. A polishing pad was produced from thethus obtained resin sheet. On observing the cross section with anoptical microscope, no interstices were found in the powdered filterpaper.

Example 50

Forty parts by weight of ultrafine fibers having a core and sheathstructure (30 μm in diameter, comprising polystyrene for the matrix, andhaving nominal water content of 5%) using Nylon 66 as the core and cutto a length of 3 mm (having an aspect ratio of about 100) was mixed with60 parts by weight of a material containing mixed therein “Artfirmer”(TA-1327, produced by Sanyo Chemical Industries, Inc.) at apredetermined mixing ratio, and the resulting mixture was fed into a40-cm square mold. After defoaming at 100° C., the product was heated at165° C. to obtain a resin sheet. A polishing pad was produced from thethus obtained resin sheet. On observing the cross section with anoptical microscope, no interstices were found in the ultrafine fibershaving a core and sheath structure using Nylon 66 as the core.

Example 51

Thirty-five parts by weight of wool (having nominal water content of15%) cut to a length of 3 mm was mixed with 65 parts by weight of akneaded product obtained from 51 parts by weight of a two-partpolyurethane resin C-4421 (manufactured by Nippon Polyurethane IndustryCo., Ltd.) and 49 parts by weight of N-4276 (manufactured by NipponPolyurethane Industry Co., Ltd.). After vacuum defoaming, the productwas fed into a 40-cm square mold and heated at 85° C. to obtain a resinsheet. On observing the cross section with an optical microscope, nointerstices were found in the wool.

Example 52

Eighteen parts by weight of a powdered filter paper (having nominalwater content of 11% and an aspect ratio of about 250) manufactured byTosco Co., Ltd. was kneaded with liquid phenolic resin (PR-53717, aproduct of Sumitomo Durez K.K.) in such a manner that the dry weight maybecome 82 parts by weight. After drying, the resulting product wasshaped under pressure of 4 MPa at 170° C. for 20 minutes to obtain asheet 1.2 mm in thickness. A polishing pad was produced from the thusobtained resin sheet. On observing the cross section with an opticalmicroscope, interstices were observed in the powdered filter paper.

Example 53

A powdered filter paper (having nominal water content of 11% and anaspect ratio of about 250) manufactured by Tosco Co., Ltd. wasuniaxially kneaded at 160° C. with polypropylene (manufactured byMitsubishi Chemicals Co., Ltd.) to obtain a compound in such a mannerthat the former may account for 2.5 wt %. By using pellets cut to alength of 3 mm, hot press molding was performed at 185° C. by using a40-cm square mold. A polishing pad was produced from the resin sheetthus obtained. On observing the cross section with an opticalmicroscope, no interstices were observed in the powdered filter paper.

Example 54

The same procedure as that described in Example 48 was followed, exceptfor mixing, in addition to the powdered filter paper, 3 parts by weightof silica particles having pores 1 μm in pore diameter. A resin sheetwas shaped, and a polishing pad was produced from the resulting resinsheet. On observing the cross section with an optical microscope, nointerstices were found in the powdered filter paper.

Examples 55 to 60

The same procedures as described in Examples 46 to 48, as well as 50 to52 were followed to obtain polishing pad each, except for adding 0.8parts by weight each of xanthane rubber as a hydrophilic water-solubleresin.

Example 61

Eighteen parts by weight of a powdered filter paper (having nominalwater content of 11% and an aspect ratio of about 250) manufactured byTosco Co., Ltd. was mixed with 3 parts by weight of silica particleshaving pores 1 μm in pore diameter, and the resulting product wasimpregnated with liquid phenolic resin (PR-53717, a product of SumitomoDurez K.K.) in such a manner that the dry weight ratio may become 79parts by weight. After drying, the resulting product was shaped underpressure of 3.5 MPa at 170° C. for 20 minutes to obtain a sheet 1.2 mmin thickness. A polishing pad was produced from the thus obtained resinsheet. On observing the cross section with an optical microscope, nointerstices were observed in the powdered filter paper.

Example 62

Forty parts by weight of ultrafine fibers having a core and sheathstructure (30 μm in diameter, comprising polystyrene for the matrix, andhaving nominal water content of 5%) using Nylon 66 as the core and cutto a length of 3 mm (having an aspect ratio of 100) was mixed with 30parts by weight of silica particles having pores 1 μm in pore diameter,and the resulting product was mixed with liquid phenolic resin(PR-55123, a product of Sumitomo Durez K.K.) at a dry weight of 30 partsby weight. The mixture was then fed into a 40-cm square mold, and afterdrying at 70° C., the product was heated at 165° C. to obtain a resinsheet. A polishing pad was produced from the thus obtained resin sheet.On observing the cross section with an optical microscope, intersticeswere found in the ultrafine fibers having a core and sheath structureusing Nylon 66 as the core.

Example 63

The same procedure as described in Example 52 was followed, except forcontrolling pressure reduction during shaping the resin sheet to forminterstices in the craft paper. A polishing pad was produced from thethus obtained resin sheet.

Example 64

A polishing resin sheet was fabricated by following the same procedureas that described in Example 52, except for further adding 2 parts byweight of xanthane rubber as a hydrophilic water-soluble resin. Apolishing pad was produced from thus obtained resin sheet. On observingthe cross section with an optical microscope, interstices were found inthe powdered filter paper.

Comparative Example 11

Polyethylene terephthalate fiber (a product of Toray Industries, Inc.,having a pore diameter of 13 μm and cut to a length of 13 μm, with anaspect ratio of 1 and nominal water content of 0.4%) was mixed withliquid phenolic resin (PR-55123, a product of Sumitomo Durez K.K.) at adry weight of 45 parts by weight. The resulting product was then shapedunder pressure of 3.5 MPa at 170° C. for 20 minutes to obtain a sheet1.2 mm in thickness. A polishing pad was produced from the thus obtainedresin sheet. On observing the cross section with an optical microscope,no interstices were observed in the powdered filter paper. Nointerstices were observed in the matrix.

Comparative Example 12

Polypropylene fiber (having a normal water content of 0% a diameter of13 μm and a length of 100 μm, with an aspect ratio of 7.7) was mixedwith 97.5 parts by weight of a 999/1 mixture of MMA (methylmethacrylate)/AIBN (azobis(isobutyronitrile)), and the resulting productwas allowed to polymerize between plates. A polishing pad was producedfrom the resin sheet thus obtained. On observing the cross section withan optical microscope, no interstices were observed in the polypropylenefibers.

TABLE 3 Evaluation of Planrization Flexural Modulus Polishing rate of(Polishing Measurement of of Elasticity D hardness Dust adhesion Scratchflaws Oxide film time/step height) Dishing (GPa) (degrees) (particles)(counts) (nm/min) (min/nm) (um) Examples 46 2.6 89 313 2 213 5/34 0.0447 0.8 73 244 2 62 5/45 0.04 48 3.6 89 334 1 87 5/33 0.04 49 2.7 85 2291 109 5/34 0.04 50 2.8 86 258 2 116 5/33 0.04 51 2.1 77 211 0 116 5/330.04 52 5.7 89 299 2 103 5/29 0.03 53 0.8 73 335 3 66 5/45 0.04 54 5.289 248 2 99 4/34 0.03 55 2.6 88 295 2 213 5/36 0.03 56 0.8 73 221 2 624/34 0.02 57 3.6 90 258 1 87 5/42 0.04 58 2.6 85 238 1 112 5/31 0.04 592.1 76 187 0 108 5/30 0.03 60 5.7 89 269 2 87 5/22 0.03 61 6.2 90 283 3107 4/29 0.03 62 10.5 92 299 4 114 4/27 0.03 63 5.6 89 288 2 105 5/290.04 64 5.1 87 223 2 85 5/20 0.03 Comp 11 3.8 90 3,473 11 74 5/44 0.05Ex 12 3.5 89 4,331 321 259 5/31 0.03(On the Effect of Nanocomposites)

Example 65

Nanocomposite was prepared by mixing silica particles 70 nm in diameterat a weight ratio of 40 wt % with polyhexamethyleneazipamide. The30:40:30 mixture of thenanocomposite/polyhexamethyleneazipamide/ADVANTEK powdered filter paper(E type) thus prepared was shaped by hot pressing at 200° C. for 15minutes using a 40-cm square mold. The dust adhesion test was performedon the thus obtained resin sheet. As a result, 251 dust particles werefound. The D hardness was 93 degrees. The polishing rate of oxide filmwas 152 nm/min. On evaluating dishing as fixed abrasive pad, a favorablevalue of 182 nm was obtained. On evaluating dishing as a conventionalpad, a favorable value of 288 nm was obtained.

Example 66

A mixture comprising 30 wt % of powdered filter paper (E type)manufactured by ADVANTEK Co., Ltd. and 70 wt % of a mixture of 17 wt %of an epoxy resin, 13 wt % of a phenolic resin, and 70 wt % of finesilica particles 2 μm in diameter, was subjected to hot press molding at185° C. using a 40-cm square mold. The dust adhesion test was performedon the thus obtained resin sheet.

As a result, 215 dust particles were found. The D hardness was 95degrees. The polishing rate of oxide film was 162 nm/min. On evaluatingdishing as fixed abrasive pad, a favorable value of 98 nm was obtained.On evaluating dishing as a conventional pad, a favorable value of 235 nmwas obtained.

Comparative Example 13

A commercially available polishing pad (“IC-1000”, a X-Ygroove-processed product manufactured by Rodel Inc., 1.2 mm inthickness, 2.0 mm in width, 0.5 mm in depth, and 15 mm in pitch) wassubjected to a dust adhesion test. As a result, 208 dusts were observed.The D hardness was found to be 63 degrees. The polishing rate of oxidefilms as 113 nm/min. On evaluating dishing as a conventional pad, anunfavorable value of 396 nm was obtained. Measurement was unfeasible incase of evaluating dishing as a fixed abrasive pad, because the stepsremained as they are even after 10 minutes.

Example 67

A mixture comprising 30 wt % of powdered filter paper (E type)manufactured by ADVANTEK Co., Ltd., 5 wt % of a powder of bariumcarbonate (consisting of particles 60 nm in diameter), and 65 wt % of amixture of 17 wt % of an epoxy resin, 13 wt % of a phenolic resin, and70 wt % of fine silica particles 2 μm in diameter, was subjected to hotpress molding at 185° C. using a 40-cm square mold. The dust adhesiontest was performed on the thus obtained resin sheet.

As a result, 233 dust particles were found. The D hardness was 95degrees. The polishing rate of oxide film was 165 nm/min. On evaluatingdishing as fixed abrasive pad, a favorable value of 90 nm was obtained.On evaluating dishing as a conventional pad, a favorable value of 243 nmwas obtained.

Comparative Example 14

The same procedures as described in Examples 65, and the pellets ofpolyhexamethyleneazipamide were subjected to hot press molding at 200°C. for fifteen minutes using a 40-cm square mold. The dust adhesion testwas performed on the thus obtained resin sheet. As a result, 425 dustparticles were found. The D hardness was 73 degrees. The polishing rateof oxide film was 80 nm/min. On evaluating dishing as a conventionalpad, unfavorable value of 334 nm was obtained. Measurement wasunfeasible in case of evaluating dishing as a fixed abrasive pad,because the steps remained as they are even after 10 minutes. (On theeffect that the change in centerline average roughness Ra fall in arange of 0.2 μm or less)

Example 68

Two sheets of filter paper 17 chr produced by Whatman Corporation weresuperposed, and the resulting product was impregnated with liquidphenolic resin (PR-53123, a product of Sumitomo Durez K.K.) to yield adry weight ratio of 50 wt %. After drying, the resulting product wasshaped under pressure of 3.5 MPa at 170° C. for 20 minutes to obtain asheet 1.8 mm in thickness. Thus obtained resin sheet was processed to asheet 1.2 mm in thickness and having X-Y grooves processed thereon.Measurement of the centerline average roughness Ra was performed. As aresult, Ra value after dressing was found to be 3.550 μm, the changeafter polishing single wafer was found to be 0.017 μm, and the changeafter polishing 5 wafers was found to be 0.019 μm. The D hardness wasfound to be 88 degrees. The polishing rate of the oxide film for thefirst wafer was found to be 62 nm/min, and that for the fifth wafer wasfound to be 63 nm/min. As a result, it has been found that the productmaintains the polishing characteristics.

Example 69

A filter paper powder (E type) produced by ADVANTEK Co. Ltd. wasuniaxially kneaded and compounded with “Surlyn” (1705, product of MitsuiDuPont Polychemicals, K.K.) at 165° C. in such a manner that the powderpaper should account for 30% by weight. Pellets cut into 3 mm in lengthwere hot pressed at 185° C. in a 40-cm square mold. Thus obtained resinsheet was processed to a sheet 1.2 mm in thickness and having X-Ygrooves processed thereon. Measurement of the centerline averageroughness Ra was performed. As a result, Ra value after dressing wasfound to be 2.550 μm, the change after polishing single wafer was foundto be 0.112 μm, and the change after polishing 5 wafers was found to be0.155 μm. The D hardness was found to be 63 degrees. The polishing rateof the oxide film for the first wafer was found to be 52 nm/min, andthat for the fifth wafer was found to be 58 nm/min. As a result, it hasbeen found that the product maintains the polishing characteristics.

Comparative Example 15

A 40-cm square “Axtar” (a product of Toray Industries, Inc.; a non-wovenmade of polyethylene terephthalate filaments, density 280 g/m²) wasimpregnated with liquid phenolic resin (PR-53123, a product of SumitomoDurez K.K.) at a dry weight ratio of 50 wt %, dried, and shaped at 170°C. for 20 minutes under pressure of 3.5 MPa to obtain a sheet 1.2 mm inthickness. Thus obtained resin sheet was subjected to X-Y grooveprocessing, and the centerline average roughness Ra was measured. As aresult, Ra value after dressing was found to be 3.355 μm, the changeafter polishing single wafer was found to be 0.402 μm, and the changeafter polishing 5 wafers was found to be 1.015 μm. The D hardness wasfound to be 90 degrees. The polishing rate of the oxide film for thefirst wafer was found to be 111 nm/min, and that for the fifth wafer wasfound to be 58 nm/min. As a result, it has been found unfeasible tomaintain the polishing characteristics.

Example 70

A mixture comprising 30 parts of powdered filter paper (E type)manufactured by ADVANTEK Co., Ltd., 2 parts of polyvinylpyrrolidone(having a molecular weight of 10000), and 68 parts of PMMA (poly(methylmethacrylate)) was pelletized at 185° C., and shaped at 210° C. for 20minutes under pressure of 3.5 MPa to obtain a sheet 1.2 mm in thickness.Thus obtained resin sheet was subjected to X-Y groove processing, andthe centerline average roughness Ra was measured. As a result, Ra valueafter dressing was found to be 4.563 μm, the change after polishingsingle wafer was found to be 0.163 μm, and the change after polishing 5wafers was found to be 0.177 μm. The D hardness was found to be 82degrees. The polishing rate of the oxide film for the first wafer wasfound to be 91 nm/min, and that for the fifth wafer was found to be 88nm/min. As a result, it has been found possible to maintain thepolishing characteristics.

Comparative Example 16

A commercially available ABS resin sheet (a product of Toyo PlasticSeiko Co., Ltd., having a thickness of 1.2 mm) was subjected to X-Ygroove processing, and the centerline average roughness Ra was measured.As a result, Ra value after dressing was found to be 4.952 μm, thechange after polishing single wafer was found to be 0.699 μm, and thechange after polishing 5 wafers was found to be 2.377 μm. The D hardnesswas found to be 80 degrees. The polishing rate of the oxide film for thefirst wafer was found to be 110 nm/min, and that for the fifth wafer wasfound to be 68 nm/min. As a result, it has been found unfeasible tomaintain the polishing characteristics.

Comparative Example 17

A commercially available polishing pad (“IC-1000”, a X-Ygroove-processed product manufactured by Rodel Inc., 1.2 mm inthickness, 2.0 mm in width, and 0.5 mm in depth 15 mm in pitch) wassubjected to the measurement of centerline average roughness Ra. As aresult, Ra value after dressing was found to be 4.313 μm, the changeafter polishing single wafer was found to be 0.238 μm, and the changeafter polishing 5 wafers was found to be 0.863 μm. The D hardness wasfound to be 63 degrees. The polishing rate of the oxide film for thefirst wafer was found to be 113 nm/min, and that for the fifth wafer wasfound to be 88 nm/min. As a result, it has been found unfeasible tomaintain the polishing characteristics.

(On the Effect of Water Absorptivity and the Rate of Water Absorption)

The evaluation results on dust adhesion and scratch flaw generation,water absorptivity and the rate of water absorption are given in Table4.

Example 71

A varnish was prepared by dissolving 100 parts of a 95/5 mixture of anepoxy resin Epikote 180S65 (product of Yuka Shell Epoxy K.K.)/SR-GLG(product of Sakamoto Yakuhin K.K.) and 4 parts of a curing agent EpicureEMI-24 (product of Yuka Shell Epoxy K.K.) in methyl ethyl ketone. Acraft paper (having nominal water content of 10%) 0.25 mm in thicknesswas impregnated with the varnish thus prepared at a dry resin weightratio of 45 wt %. After drying, 6 sheets of the resulting product wereshaped at 170° C. for 20 minutes under pressure of 1 MPa to obtain asheet 1.2 mm in thickness.

Example 72

Two-part polyurethane resin KC-380 (product of Nippon PolyurethaneIndustry Co., Ltd.) and KN-585 (product of Nippon Polyurethane IndustryCo., Ltd.) were kneaded at a weight ratio of 70 wt % and 30 wt %,respectively, and powdered filter paper (KC-FLOCK produced by NipponPapermaking Industry Co., Ltd., 400-mesh size, having nominal watercontent of 11%) was further kneaded at a weight ratio of 25 parts byweight. After defoaming, the product was allowed to set inside the mold,and by cutting, 1.2 mm thick polyurethane sheet was produced.

Examples 73 to 77

Commercially available phenolic laminate sheets, FL-1041, FL-1051,FL-1065 (products of Nimura Kagaku Kogyo Co., Ltd.) and PS-1031S (RishoKogyo Co., Ltd.), and paper epoxy laminate resin sheet ES-1192 (productof Risho Kogyo Co., Ltd.) were used to shape resin sheets 1.2 mm inthickness.

Evaluation was made on the order above.

Example 78

Two-part polyurethane resin KC-362 (product of Nippon PolyurethaneIndustry Co., Ltd.) and N-4276 (product of Nippon Polyurethane IndustryCo., Ltd.) were kneaded at a weight ratio of 51 wt % and 49 wt %,respectively, and powdered filter paper (KC-FLOCK produced by NipponPapermaking Industry Co., Ltd., 400-mesh size, having nominal watercontent of 11%) was further kneaded at a weight ratio of 25 parts byweight. After defoaming, the product was allowed to set inside the mold,and by cutting, 1.2 mm thick polyurethane sheet was produced.

Comparative Example 18

A 1.2 mm thick resin sheet was shaped by using a commercially availableglass cloth epoxy laminate sheet ES-3350 (Risho Kogyo Co., Ltd.)

TABLE 4 One-hour water Water absorption rate Flexural Modulus ofabsorptivity in 5 minutes Dust adhesion Scratch flaws Elasticity Dhardness (%) (%/hr) (counts) (counts) (GPa) (degrees) Examples 71 6.637.1   43 0 4.8 88.0 72 1.9 6.7  69 1 1.8 75.0 73 0.5 2.1 267 2 5.6 89.074 0.6 2.2 245 2 5.4 89.0 75 0.7 2.6 229 1 5.2 89 76 0.5 1.8 251 2 7.890 77 0.2 0.9 277 2 10.2  90 78 0.3 1.0 271 2 1.9 77 Comp Ex. 18 0.1 0.3Uncountable Uncountable 12 92

INDUSTRIAL APPLICABILITY

The present invention reduces the scratch flaws and the dust adhesionthat generate on the surface of the object to be polished, whileincreasing the polishing rate and minimizing dishing and erosion. Hence,the present invention is applicable to the field of surface polishing ofsemiconductor thin films.

1. A polishing pad comprising a resin matrix having a domain of asubstantially water-insoluble hydrophilic polymer dispersed therein. 2.A polishing pad as claimed in claim 1, wherein the substantiallywater-insoluble hydrophilic polymer comprises a domain structure havingan area of 1×10⁻⁶ m² or smaller.
 3. A polishing pad as claimed in claim1, wherein the substantially water-insoluble hydrophilic polymercomprises particles or fibrous material having a water absorptivity of5000% or lower.
 4. A polishing pad as claimed in claim 3, wherein saidparticles or fibrous material are mixed in such a manner to account for4 wt. % or higher but not higher than 60 wt. %.
 5. A polishing pad asclaimed in claim 1, wherein the substantially water-insolublehydrophilic polymer is a sheet material, and comprises a laminate of acomplex structure with an organic polymer matrix.
 6. A polishing pad asclaimed in claim 5, wherein the sheet material comprises at least one ofnon-woven, textile, woven, felt porous membrane, film, and sponge sheet.7. A polishing pad as claimed in claim 5, wherein layers constituting alaminate have a thickness of 1 μm or more.
 8. A polishing pad as claimedin claim 5, wherein the resin content or the type of the resin of theresin matrix differs from layer to layer.
 9. A polishing pad as claimedin claim 7, wherein the thickness or the type of the sheet materialdiffers from layer to layer.
 10. A polishing pad as claimed in claim 5,wherein the sheet material accounts for 3 wt. % or more.
 11. A polishingpad as claimed in claim 1, wherein the domain of a substantiallywater-insoluble hydrophilic polymer mixed in resin matrix comprises afibrous material having an aspect ratio of 5 or higher or particlesformed from a composite of the fibrous materials.
 12. A polishing pad asclaimed in claim 1, wherein the substantially water-insolublehydrophilic polymer has nominal water content of 3% or higher.
 13. Apolishing pad as claimed in claim 1, wherein the domain of asubstantially water-insoluble hydrophilic polymer mixed in a resinmatrix is mixed in such a manner substantially free from interstices ofthe complex structure.
 14. A polishing pad as claimed in claim 1,wherein the matrix constituting the pad is made of a thermosettingresin.
 15. A polishing pad as claimed in claim 1, wherein the pad hasinterstices in addition to the domain of a substantially water-insolublehydrophilic polymer mixed in a resin matrix.
 16. A polishing pad asclaimed in claim 1, wherein the pad comprises inorganic fine particles.17. A polishing pad as claimed in claim 1, wherein the pad comprisesorganic-inorganic nanocomposite and/or barium carbonate particles.
 18. Apolishing pad as claimed in claim 17, wherein the organic-inorganicnanocomposite is at least one selected from a combination of a phenolicresin and silica particles, a combination of an epoxy resin and silicaparticles, and a combination of a polyamide resin and silica particles.19. A polishing pad as claimed in claim 1, wherein the pad furthercomprises a water-soluble substance.
 20. A polishing pad as claimed inclaim 19, wherein the water-soluble substance accounts for 0.01 wt % to10 wt %.
 21. A polishing pad as claimed in claim 1, wherein the pad hasa D hardness of 65 or higher.
 22. A polishing pad as claimed in claim 1,wherein the pad has a flexural modulus of elasticity of 0.5 GPa orhigher but not higher than 100 GPa.
 23. A polishing pad as claimed inclaim 1, wherein the pad has a one-hour water absorptivity of 0.8% orhigher but not higher than 15%.
 24. A polishing pad as claimed in claim1, wherein the pad has a water absorption rate within 5 minutes fromcontact with water is 3%/hr or higher.
 25. A polishing apparatuscomprising a polishing pad claimed in claim 1.